restrictedpython_code_eval.py

# Copyright 2020 The HuggingFace Datasets Authors and the current dataset script contributor.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""This is an implementation of the `CodeEval` metric that uses `RestrictedPython`
to exectue the untrusted code returned by the model.
Lightly adapted and mostly copied verbatim from the implementation in `evaluate`. 
"""
import ast
import contextlib
import copy
import faulthandler
import itertools
import importlib
import importlib.util
import io
import multiprocessing
import os
import platform
import signal
import sys
import tempfile
import types
from typing import Optional, Dict, List, Any


from collections import Counter, defaultdict
from concurrent.futures import ThreadPoolExecutor, as_completed

import evaluate
# from evaluate.metrics import code_eval
import datasets
import numpy as np
from RestrictedPython import compile_restricted, safe_builtins, limited_builtins, utility_builtins, RestrictingNodeTransformer
from RestrictedPython.transformer import copy_locations, IOPERATOR_TO_STR, FORBIDDEN_FUNC_NAMES
from RestrictedPython.Eval import default_guarded_getiter, default_guarded_getitem
from RestrictedPython.Guards import guarded_iter_unpack_sequence, safer_getattr, guarded_unpack_sequence


# patch their list implementation to allow empty lists and tuples
def limited_list(seq=None):
    if isinstance(seq, str):
        # raise TypeError('cannot convert string to list')
        return [c for c in seq]
    return list(seq) if seq is not None else list()


limited_builtins['list'] = limited_list


def limited_tuple(seq=None):
    if isinstance(seq, str):
        # raise TypeError('cannot convert string to tuple')
        return tuple([c for c in seq])
    return tuple(seq) if seq is not None else tuple()


limited_builtins['tuple'] = limited_tuple


def limited_range(iFirst, *args):
    # limited range function from Martijn Pieters
    RANGELIMIT = 10000
    if not len(args):
        iStart, iEnd, iStep = 0, iFirst, 1
    elif len(args) == 1:
        iStart, iEnd, iStep = iFirst, args[0], 1
    elif len(args) == 2:
        iStart, iEnd, iStep = iFirst, args[0], args[1]
    else:
        raise AttributeError('range() requires 1-3 int arguments')
    if iStep == 0:
        raise ValueError('zero step for range()')
    iLen = int((iEnd - iStart) / iStep)
    if iLen < 0:
        iLen = 0
    if iLen >= RANGELIMIT:
        raise ValueError(
            'To be created range() object would be too large, '
            'in RestrictedPython we only allow {limit} '
            'elements in a range.'.format(limit=str(RANGELIMIT)),
        )
    return range(iStart, iEnd, iStep)


limited_builtins['range'] = limited_range


ALLOWED_UNDERSCORE_NAMES = ['__add__']


def safer_getattr_allowing_string_format(object, name, default=None, getattr=getattr):
    """Getattr implementation allowing str.format(), but preventing access to
    private attributes.

    format() is considered harmful, so use at own risk:
    http://lucumr.pocoo.org/2016/12/29/careful-with-str-format/

    """
    if name.startswith('_') and name not in ALLOWED_UNDERSCORE_NAMES:
        raise AttributeError(
            '"{name}" is an invalid attribute name because it '
            'starts with "_"'.format(name=name)
        )
    return getattr(object, name, default)


class AllowAugmentedAssignRestrictingTransformer(RestrictingNodeTransformer):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        
    def visit_AugAssign(self, node):
        # allow += and similar operations for list indices
        if isinstance(node.target, ast.Subscript):
            # new_name = copy.deepcopy(node.target.value)
            # new_name.ctx = ast.Load()  # type: ignore

            new_subscript = copy.deepcopy(node.target)
            new_subscript.ctx = ast.Load()
            if hasattr(new_subscript.value, 'ctx'):
                new_subscript.value.ctx = ast.Load()  # type: ignore

            new_node = ast.Assign(
                targets=[node.target],
                value=ast.Call(
                    func=ast.Name('_inplacevar_', ast.Load()),
                    args=[
                        ast.Str(IOPERATOR_TO_STR[type(node.op)]),
                        new_subscript,
                        # ast.Subscript(
                        #     value=new_name,
                        #     slice=node.target.slice,
                        #     ctx=ast.Load(),
                        # ),
                        node.value
                    ],
                    keywords=[]))

            copy_locations(new_node, node)
            return new_node
        
        return super().visit_AugAssign(node)


class AllowAugmentedAssignAndUnderscoreVariableNamesRestrictingTransformer(AllowAugmentedAssignRestrictingTransformer):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def check_name(self, node, name, allow_magic_methods=False):
        if name is None:
            return

        if name.startswith('_'):
            # Verify it doesn't do anything else that's not allowed
            if not name.endswith('__roles__') and not name in FORBIDDEN_FUNC_NAMES:
                return
        
        # Otherwise, flow to parent logic
        return super().check_name(node, name, allow_magic_methods)


# TODO: Add BibTeX citation
_CITATION = """\
@InProceedings{huggingface:module,
title = {A great new module},
authors={huggingface, Inc.},
year={2020}
}
"""

# TODO: Add description of the module here
_DESCRIPTION = """\
This module implements the same logic as the baseline `code_eval` module but using RestrictedPython.
"""


# TODO: Add description of the arguments of the module here
_KWARGS_DESCRIPTION = """
Calculates how good are predictions given some references, using certain scores
Args:
    predictions: list of candidates to evaluate. Each candidates should be a list
        of strings with several code candidates to solve the problem.
    references: a list with a test for each prediction. Each test should evaluate the
        correctness of a code candidate.
    k: number of code candidates to consider in the evaluation (Default: [1, 10, 100])
    num_workers: number of workers used to evaluate the canidate programs (Default: 4).
    timeout:
    use_safe_builtins: a bool indicating whether to use the `RestrictedPython.safe_builtins`
    use_limited_builtins: a bool indicating whether to use the `RestrictedPython.limited_builtins`
    use_utility_builtins: a bool indicating whether to use the `RestrictedPython.utility_builtins`
    additional_globals: a optional dict of additional globals to pass to the RestrictedPython interpreter
    additional_locals: a optional dict of additional locals to pass to the RestrictedPython interpreter
    allowed_imports: an optional list of string, modules the tested code is allowed to import
    allow_str_format: a bool indicating whether to allow the use of str.format() in the tested code
    allow_underscore_variable_names: a bool indicating whether to allow the use of underscore variable names in the tested code

Returns:
    pass_at_k: dict with pass rates for each k
    results: dict with granular results of each unittest
Examples:
    >>> code_eval = evaluate.load("RestrictedPython_code_eval")
    >>> test_cases = ["assert add(2,3)==5"]
    >>> candidates = [["def add(a,b): return a*b", "def add(a, b): return a+b"]]
    >>> pass_at_k, results = code_eval.compute(references=test_cases, predictions=candidates, k=[1, 2])
    >>> print(pass_at_k)
    {'pass@1': 0.5, 'pass@2': 1.0}
"""

_WARNING = """
################################################################################
                                  !!!WARNING!!!
################################################################################
The "code_eval" metric executes untrusted model-generated code in Python.
Although it is highly unlikely that model-generated code will do something
overtly malicious in response to this test suite, model-generated code may act
destructively due to a lack of model capability or alignment.
Users are strongly encouraged to sandbox this evaluation suite so that it
does not perform destructive actions on their host or network. For more
information on how OpenAI sandboxes its code, see the paper "Evaluating Large
Language Models Trained on Code" (https://arxiv.org/abs/2107.03374).

Once you have read this disclaimer and taken appropriate precautions,
set the environment variable HF_ALLOW_CODE_EVAL="1". Within Python you can to this
with:

>>> import os
>>> os.environ["HF_ALLOW_CODE_EVAL"] = "1"

################################################################################\
"""

# TODO: who has the copyright?
_LICENSE = """The MIT License

Copyright (c) OpenAI (https://openai.com)

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE."""

@evaluate.utils.file_utils.add_start_docstrings(_DESCRIPTION, _KWARGS_DESCRIPTION)
class RestrictedPythonCodeEval(evaluate.Metric):
    """Exactly the same as the built in `code_eval` module, but using restricted python"""

    def _info(self):
        # TODO: Specifies the evaluate.EvaluationModuleInfo object
        return evaluate.MetricInfo(
            # This is the description that will appear on the modules page.
            module_type="metric",
            description=_DESCRIPTION,
            citation=_CITATION,
            inputs_description=_KWARGS_DESCRIPTION,
            # This defines the format of each prediction and reference
            features=datasets.Features({
                'predictions': datasets.Sequence(datasets.Value("string")),
                'references': datasets.Value('string'),
            }),
            # Homepage of the module for documentation
            homepage="http://module.homepage",
            # Additional links to the codebase or references
            codebase_urls=["http://github.com/path/to/codebase/of/new_module"],
            reference_urls=["http://path.to.reference.url/new_module"]
        )

    def _compute(self, predictions, references, k=[1, 10, 100], num_workers=4, timeout=3.0,
                 use_safe_builtins: bool = True, use_limited_builtins: bool = True, use_utility_builtins: bool = True,
                 additional_globals: Optional[Dict[str, Any]] = None, additional_locals: Optional[Dict[str, Any]] = None,
                 allowed_imports: Optional[List[str]] = None, allow_str_format: bool = False,
                 allow_underscore_variable_names: bool = False):
        """Returns the scores"""

        if os.getenv("HF_ALLOW_CODE_EVAL", 0) != "1":
            raise ValueError(_WARNING)

        if os.name == "nt":
            raise NotImplementedError("This metric is currently not supported on Windows.")

        with ThreadPoolExecutor(max_workers=num_workers) as executor:
            futures = []
            completion_id = Counter()
            n_samples = 0
            results = defaultdict(list)

            for task_id, (candidates, test_case) in enumerate(zip(predictions, references)):
                for candidate in candidates:
                    test_program = candidate + "\n" + test_case
                    args = (
                        test_program, timeout, task_id, completion_id[task_id], 
                        use_safe_builtins, use_limited_builtins, use_utility_builtins,
                        additional_globals, additional_locals, 
                        allowed_imports, allow_str_format, allow_underscore_variable_names
                    )
                    future = executor.submit(_check_correctness, *args)
                    futures.append(future)
                    completion_id[task_id] += 1
                    n_samples += 1

            for future in as_completed(futures):
                result = future.result()
                results[result["task_id"]].append((result["completion_id"], result))

        total, correct = [], []
        for result in results.values():
            result.sort()
            passed = [r[1]["passed"] for r in result]
            total.append(len(passed))
            correct.append(sum(passed))
        total = np.array(total)
        correct = np.array(correct)

        ks = k
        pass_at_k = {f"pass@{k}": estimate_pass_at_k(total, correct, k).mean() for k in ks if (total >= k).all()}

        return pass_at_k, results
            

def estimate_pass_at_k(num_samples, num_correct, k):
    """Estimates pass@k of each problem and returns them in an array."""

    def estimator(n: int, c: int, k: int) -> float:
        """Calculates 1 - comb(n - c, k) / comb(n, k)."""
        if n - c < k:
            return 1.0
        return 1.0 - np.prod(1.0 - k / np.arange(n - c + 1, n + 1))  # type: ignore

    if isinstance(num_samples, int):
        num_samples_it = itertools.repeat(num_samples, len(num_correct))
    else:
        assert len(num_samples) == len(num_correct)
        num_samples_it = iter(num_samples)

    return np.array([estimator(int(n), int(c), k) for n, c in zip(num_samples_it, num_correct)])



def _check_correctness(check_program, timeout, task_id, completion_id,
                       use_safe_builtins: bool = True, use_limited_builtins: bool = True, use_utility_builtins: bool = True,
                       additional_globals: Optional[Dict[str, Any]] = None, additional_locals: Optional[Dict[str, Any]] = None,
                       allowed_imports: Optional[List[str]] = None, allow_str_format: bool = False,
                       allow_underscore_variable_names: bool = False):
    """
    Evaluates the functional correctness of a completion by running the test
    suite provided in the problem.

    :param completion_id: an optional completion ID so we can match
        the results later even if execution finishes asynchronously.
    """
    manager = multiprocessing.Manager()
    result = manager.list()

    args = (
        check_program, result, timeout, 
        use_safe_builtins, use_limited_builtins, use_utility_builtins,
        additional_globals, additional_locals, 
        allowed_imports, allow_str_format, allow_underscore_variable_names,
    )
    p = multiprocessing.Process(target=_unsafe_execute, args=args)
    p.start()
    p.join(timeout=timeout + 1)
    if p.is_alive():
        p.kill()


    if not result:
        result.append("Result evaluates to False (probably timed out)")

    out_dict = dict(
        task_id=task_id,
        passed=result[0] == "passed",
        result=result[0],
        completion_id=completion_id,
    )

    if 'failed' in result[0] and len(result) > 1:
        exc = result[1]
        out_dict["exception_type"] = type(exc).__name__
        out_dict["exception_description"] = str(exc)

    return out_dict


ALLOWED_SYS_NAMES = ['maxsize']


class AllowListImporter:
    def __init__(self, allowed_imports: List[str]):
        self.allowed_imports = allowed_imports
        
    def __call__(self, name, globals=None, locals=None, fromlist=(), level=0):
        if name.startswith('.'):
            raise ImportError("Relative imports are not allowed.")
        
        if '.' in name:
            package_name, _ = name.split('.', 1)

        else:
            package_name = name
        
        if package_name in self.allowed_imports:
            return importlib.__import__(name, globals, locals, fromlist, level)


def _default_write_(obj):
    if isinstance(obj, types.ModuleType):
        raise ValueError("Modules are not allowed in to be written to.")
    
    return obj


class DefaultPrinter:
    def __init__(self, _getattr_=None, *args, **kwargs):
        self._getattr_ = _getattr_
        self.txt = []

        self.args = args
        self.kwargs = kwargs

    def write(self, text):
        self.txt.append(text)
        print(text)

    def __call__(self):
        return ''.join(self.txt)

    def _call_print(self, *objects, **kwargs):
        if kwargs.get('file', None) is None:
            kwargs['file'] = self
        else:
            self._getattr_(kwargs['file'], 'write')  # type: ignore

        print(*objects, **kwargs)



def _unsafe_execute(check_program, result, timeout, 
                    use_safe_builtins: bool = True, use_limited_builtins: bool = True, use_utility_builtins: bool = True,
                    additional_globals: Optional[Dict[str, Any]] = None, additional_locals: Optional[Dict[str, Any]] = None,
                    allowed_imports: Optional[List[str]] = None, allow_str_format: bool = False,
                    allow_underscore_variable_names: bool = False):

    with create_tempdir():

        # These system calls are needed when cleaning up tempdir.
        import os
        import shutil

        rmtree = shutil.rmtree
        rmdir = os.rmdir
        chdir = os.chdir

        # Disable functionalities that can make destructive changes to the test.
        reliability_guard()

        # Run program.
        try:
            builtins = {}
            if use_safe_builtins:
                builtins.update(safe_builtins)
            if use_limited_builtins:
                builtins.update(limited_builtins)
            if use_utility_builtins:
                builtins.update(utility_builtins)

            exec_globals = {'__builtins__': builtins}
            
            if additional_globals is None:
                additional_globals = {}

            for key, glob in additional_globals.items():
                if key not in exec_globals:
                    exec_globals[key] = glob
                
                else:
                    exec_globals[key].update(glob)

            if allowed_imports is not None:
                if '__import__' in exec_globals['__builtins__']:
                    raise ValueError("Cannot specify allowed_imports when __import__ is in additional_globals.")
                
                exec_globals['__builtins__']['__import__'] = AllowListImporter(allowed_imports)

            if allow_str_format:
                exec_globals['getattr'] = safer_getattr_allowing_string_format  # type: ignore
                exec_globals['__builtins__']['getattr'] = safer_getattr_allowing_string_format  

            if '__metaclass__' not in exec_globals:
                exec_globals['__metaclass__'] = type  # type: ignore

            if '__name__' not in exec_globals:
                exec_globals['__name__'] = '__main__'  # type: ignore
            
            if '_getiter_' not in exec_globals:
                exec_globals['_getiter_'] = default_guarded_getiter  # type: ignore

            if '_iter_unpack_sequence_' not in exec_globals:
                exec_globals['_iter_unpack_sequence_'] = guarded_iter_unpack_sequence  # type: ignore

            if '_unpack_sequence_' not in exec_globals:
                exec_globals['_unpack_sequence_'] = guarded_unpack_sequence  # type: ignore

            if '_getitem_' not in exec_globals:
                exec_globals['_getitem_'] = default_guarded_getitem  # type: ignore

            if 'getattr' not in exec_globals:
                exec_globals['getattr'] = safer_getattr  # type: ignore

            if '_write_' not in exec_globals:
                exec_globals['_write_'] = _default_write_  # type: ignore

            if '_inplacevar_' not in exec_globals:
                exec_globals['_inplacevar_'] = protected_inplacevar  # type: ignore

            if '_print_' not in exec_globals:
                exec_globals['_print_'] = DefaultPrinter  # type: ignore

            if '_apply_' not in exec_globals:
                exec_globals['_apply_'] = _apply  # type: ignore

            with swallow_io():
                policy_class = AllowAugmentedAssignAndUnderscoreVariableNamesRestrictingTransformer if allow_underscore_variable_names else AllowAugmentedAssignRestrictingTransformer


                with time_limit(timeout):
                    byte_code = compile_restricted(check_program, filename="<model output>", mode="exec", policy=policy_class)
                    exec(byte_code, exec_globals, additional_locals)
            
            result.append("passed")
        except EOFError:
            result.append("EOF error")
        except TimeoutException:
            result.append("timed out")
        except BaseException as e:
            result.append(f"failed ({type(e)}): {str(e)}")
            result.append(e)

        # Needed for cleaning up.
        shutil.rmtree = rmtree
        os.rmdir = rmdir
        os.chdir = chdir


@contextlib.contextmanager
def time_limit(seconds):
    def signal_handler(signum, frame):
        raise TimeoutException("Timed out!")

    signal.setitimer(signal.ITIMER_REAL, seconds)
    signal.signal(signal.SIGALRM, signal_handler)
    try:
        yield
    finally:
        signal.setitimer(signal.ITIMER_REAL, 0)


@contextlib.contextmanager
def swallow_io():
    stream = WriteOnlyStringIO()
    with contextlib.redirect_stdout(stream):
        with contextlib.redirect_stderr(stream):
            with redirect_stdin(stream):
                yield


@contextlib.contextmanager
def create_tempdir():
    with tempfile.TemporaryDirectory() as dirname:
        with chdir(dirname):
            yield dirname


class TimeoutException(Exception):
    pass


class WriteOnlyStringIO(io.StringIO):
    """StringIO that throws an exception when it's read from"""

    def read(self, *args, **kwargs):
        raise OSError

    def readline(self, *args, **kwargs):
        raise OSError

    def readlines(self, *args, **kwargs):
        raise OSError

    def readable(self, *args, **kwargs):
        """Returns True if the IO object can be read."""
        return False


class redirect_stdin(contextlib._RedirectStream):  # type: ignore
    _stream = "stdin"


@contextlib.contextmanager
def chdir(root):
    if root == ".":
        yield
        return
    cwd = os.getcwd()
    os.chdir(root)
    try:
        yield
    except BaseException as exc:
        raise exc
    finally:
        os.chdir(cwd)


def reliability_guard(maximum_memory_bytes=None):
    """
    This disables various destructive functions and prevents the generated code
    from interfering with the test (e.g. fork bomb, killing other processes,
    removing filesystem files, etc.)

    WARNING
    This function is NOT a security sandbox. Untrusted code, including, model-
    generated code, should not be blindly executed outside of one. See the
    Codex paper for more information about OpenAI's code sandbox, and proceed
    with caution.
    """

    if maximum_memory_bytes is not None:
        import resource

        resource.setrlimit(resource.RLIMIT_AS, (maximum_memory_bytes, maximum_memory_bytes))
        resource.setrlimit(resource.RLIMIT_DATA, (maximum_memory_bytes, maximum_memory_bytes))
        if not platform.uname().system == "Darwin":
            resource.setrlimit(resource.RLIMIT_STACK, (maximum_memory_bytes, maximum_memory_bytes))

    faulthandler.disable()

    import builtins

    builtins.exit = None
    builtins.quit = None

    import os

    os.environ["OMP_NUM_THREADS"] = "1"

    os.kill = None
    os.system = None
    os.putenv = None
    os.remove = None
    os.removedirs = None
    os.rmdir = None
    os.fchdir = None
    os.setuid = None
    os.fork = None
    os.forkpty = None
    os.killpg = None
    os.rename = None
    os.renames = None
    os.truncate = None
    os.replace = None
    os.unlink = None
    os.fchmod = None
    os.fchown = None
    os.chmod = None
    os.chown = None
    os.chroot = None
    os.fchdir = None
    os.lchflags = None
    os.lchmod = None
    os.lchown = None
    os.getcwd = None
    os.chdir = None

    import shutil

    shutil.rmtree = None
    shutil.move = None
    shutil.chown = None

    import subprocess

    subprocess.Popen = None  # type: ignore

    __builtins__["help"] = None

    import sys

    sys.modules["ipdb"] = None  # type: ignore
    sys.modules["joblib"] = None  # type: ignore
    sys.modules["resource"] = None  # type: ignore
    sys.modules["psutil"] = None  # type: ignore
    sys.modules["tkinter"] = None  # type: ignore


""" 
Borrowed implementation of _inplacevar_ from the Zope Foundations's AccessControl module
https://github.com/zopefoundation/AccessControl/blob/f9ae58816f0712eb6ea97459b4ccafbf4662d9db/src/AccessControl/ZopeGuards.py#L530
"""

valid_inplace_types = (list, set)


inplace_slots = {
    '+=': '__iadd__',
    '-=': '__isub__',
    '*=': '__imul__',
    '/=': (1 / 2 == 0) and '__idiv__' or '__itruediv__',
    '//=': '__ifloordiv__',
    '%=': '__imod__',
    '**=': '__ipow__',
    '<<=': '__ilshift__',
    '>>=': '__irshift__',
    '&=': '__iand__',
    '^=': '__ixor__',
    '|=': '__ior__',
}


def __iadd__(x, y):
    x += y
    return x


def __isub__(x, y):
    x -= y
    return x


def __imul__(x, y):
    x *= y
    return x


def __idiv__(x, y):
    x /= y
    return x


def __ifloordiv__(x, y):
    x //= y
    return x


def __imod__(x, y):
    x %= y
    return x


def __ipow__(x, y):
    x **= y
    return x


def __ilshift__(x, y):
    x <<= y
    return x


def __irshift__(x, y):
    x >>= y
    return x


def __iand__(x, y):
    x &= y
    return x


def __ixor__(x, y):
    x ^= y
    return x


def __ior__(x, y):
    x |= y
    return x


inplace_ops = {
    '+=': __iadd__,
    '-=': __isub__,
    '*=': __imul__,
    '/=': __idiv__,
    '//=': __ifloordiv__,
    '%=': __imod__,
    '**=': __ipow__,
    '<<=': __ilshift__,
    '>>=': __irshift__,
    '&=': __iand__,
    '^=': __ixor__,
    '|=': __ior__,
}


def protected_inplacevar(op, var, expr):
    """Do an inplace operation

    If the var has an inplace slot, then disallow the operation
    unless the var an instance of ``valid_inplace_types``.
    """
    if hasattr(var, inplace_slots[op]) and \
       not isinstance(var, valid_inplace_types):
        try:
            cls = var.__class__
        except AttributeError:
            cls = type(var)
        raise TypeError(
            "Augmented assignment to %s objects is not allowed"
            " in untrusted code" % cls.__name__)
    return inplace_ops[op](var, expr)

def _apply(f, *a, **kw):
    return f(*a, **kw)