# Buggy code
def defer(self, callable, *args, **kwargs):
    """
    Register a deferred function, i.e. a callable that will be invoked after the current attempt
    at running this job concludes. A job attempt is said to conclude when the job function (or
    the Job.run method for class-based jobs) returns, raises an exception or after the process
    running it terminates abnormally. A deferred function will be called on the node that
    attempted to run the job, even if a subsequent attempt is made on another node. A deferred
    function should be idempotent because it may be called multiple times on the same node or
    even in the same process. More than one deferred function may be registered per job attempt
    by calling this method repeatedly with different arguments. If the same callable is
    registered twice, it will be called twice per job attempt.

    The functions one would typically provide here are cleanup functions that handle
    Toil-external events upon a failure within Toil (killing Docker containers, etc).

    :param function callable: The function to be run after this job.
    :param list args: The arguments to the function
    :param dict kwargs: The keyword arguments to the function
    :return: None
    """
    try:
        getattr(self, "fileStore")
    except AttributeError:
        raise RuntimeError(
            "A deferred function may only be registered from within the job it "
            'is being registered with. "%s" was illegally registered.',
            callable.__name__,
        )
    self.fileStore._registerDeferredFunction(callable, *args, **kwargs)


# Traceback (ImportError)
---TOIL WORKER OUTPUT LOG---
f006bc8b-195a-45b8-8e35-2291a2985f14    Next available file descriptor: 8
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.worker:Next available file descriptor: 8
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.jobStores.aws.jobStore:Loaded job f006bc8b-195a-45b8-8e35-2291a2985f14
f006bc8b-195a-45b8-8e35-2291a2985f14    Parsed jobWrapper
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.worker:Parsed jobWrapper
f006bc8b-195a-45b8-8e35-2291a2985f14    Got a command to run: _toil d171ba6d-1842-4f3e-998a-84c3d11cee59 /usr/local/lib/python2.7/dist-packages toil.job False
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.worker:Got a command to run: _toil d171ba6d-1842-4f3e-998a-84c3d11cee59 /usr/local/lib/python2.7/dist-packages toil.job Fals
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.job:Loading user module ModuleDescriptor(dirPath='/usr/local/lib/python2.7/dist-packages', name='toil.job', fromVirtualEnv=F
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.jobStores.aws.jobStore:Reading FileInfo(fileID='d171ba6d-1842-4f3e-998a-84c3d11cee59', ownerID='96b4d6f2-1b56-48f5-b1c4-9f0d
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.job:Getting Job from module toil.job.
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.job:Getting Config from module toil.common.
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.job:Getting defaultdict from module collections.
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.job:Getting list from module __builtin__.
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.job:Getting ModuleDescriptor from module toil.resource.
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.job:Getting set from module __builtin__.
f006bc8b-195a-45b8-8e35-2291a2985f14    INFO:toil.fileStore:Starting job (d171ba6d-1842-4f3e-998a-84c3d11cee59) with ID (d9a3bddaadfb045480c8964cb490dcba2493d8f9).
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.fileStore:CACHE: Obtained lock on file /var/lib/toil/toil-17daa335-7e62-4772-9308-53456ca4b46a/cache-17daa335-7e62-4772-9308
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.fileStore:CACHE: Released lock
f006bc8b-195a-45b8-8e35-2291a2985f14    Traceback (most recent call last):
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/local/lib/python2.7/dist-packages/toil/worker.py", line 323, in main
f006bc8b-195a-45b8-8e35-2291a2985f14        caching=not config.disableCaching)
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/local/lib/python2.7/dist-packages/toil/fileStore.py", line 109, in createFileStore
f006bc8b-195a-45b8-8e35-2291a2985f14        return fileStoreCls(jobStore, jobWrapper, localTempDir, inputBlockFn)
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/local/lib/python2.7/dist-packages/toil/fileStore.py", line 104, in __init__
f006bc8b-195a-45b8-8e35-2291a2985f14        self._setupCache()
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/local/lib/python2.7/dist-packages/toil/fileStore.py", line 624, in _setupCache
f006bc8b-195a-45b8-8e35-2291a2985f14        with self._CacheState.open(self) as cacheInfo:
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
f006bc8b-195a-45b8-8e35-2291a2985f14        return self.gen.next()
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/local/lib/python2.7/dist-packages/toil/fileStore.py", line 986, in open
f006bc8b-195a-45b8-8e35-2291a2985f14        cacheInfo = cls._load(outer.cacheStateFile)
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/local/lib/python2.7/dist-packages/toil/fileStore.py", line 999, in _load
f006bc8b-195a-45b8-8e35-2291a2985f14        cacheInfoDict = dill.load(fH)
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/local/lib/python2.7/dist-packages/dill/dill.py", line 250, in load
f006bc8b-195a-45b8-8e35-2291a2985f14        obj = pik.load()
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/lib/python2.7/pickle.py", line 864, in load
f006bc8b-195a-45b8-8e35-2291a2985f14        dispatch[key](self)
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/lib/python2.7/pickle.py", line 1096, in load_global
f006bc8b-195a-45b8-8e35-2291a2985f14        klass = self.find_class(module, name)
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/local/lib/python2.7/dist-packages/dill/dill.py", line 406, in find_class
f006bc8b-195a-45b8-8e35-2291a2985f14        return StockUnpickler.find_class(self, module, name)
f006bc8b-195a-45b8-8e35-2291a2985f14      File "/usr/lib/python2.7/pickle.py", line 1130, in find_class
f006bc8b-195a-45b8-8e35-2291a2985f14        __import__(module)
f006bc8b-195a-45b8-8e35-2291a2985f14    ImportError: No module named toil_lib.programs
f006bc8b-195a-45b8-8e35-2291a2985f14    Exiting the worker because of a failed jobWrapper on host ip-172-31-3-245
f006bc8b-195a-45b8-8e35-2291a2985f14    ERROR:toil.worker:Exiting the worker because of a failed jobWrapper on host ip-172-31-3-245
f006bc8b-195a-45b8-8e35-2291a2985f14    DEBUG:toil.jobStores.aws.jobStore:Loaded job f006bc8b-195a-45b8-8e35-2291a2985f14
f006bc8b-195a-45b8-8e35-2291a2985f14    WARNING:toil.jobWrapper:Due to failure we are reducing the remaining retry count of job f006bc8b-195a-45b8-8e35-2291a2985f14 to 0
f006bc8b-195a-45b8-8e35-2291a2985f14    WARNING:toil.jobWrapper:We have increased the default memory of the failed job to 2147483648 bytes

# Fixed code
def defer(self, function, *args, **kwargs):
    """
    Register a deferred function, i.e. a callable that will be invoked after the current
    attempt at running this job concludes. A job attempt is said to conclude when the job
    function (or the :meth:`Job.run` method for class-based jobs) returns, raises an
    exception or after the process running it terminates abnormally. A deferred function will
    be called on the node that attempted to run the job, even if a subsequent attempt is made
    on another node. A deferred function should be idempotent because it may be called
    multiple times on the same node or even in the same process. More than one deferred
    function may be registered per job attempt by calling this method repeatedly with
    different arguments. If the same function is registered twice with the same or different
    arguments, it will be called twice per job attempt.

    Examples for deferred functions are ones that handle cleanup of resources external to
    Toil, like Docker containers, files outside the work directory, etc.

    :param callable function: The function to be called after this job concludes.

    :param list args: The arguments to the function

    :param dict kwargs: The keyword arguments to the function
    """
    require(
        self.fileStore is not None,
        "A deferred function may only be registered with a "
        "job while that job is running.",
    )
    self.fileStore._registerDeferredFunction(
        DeferredFunction.create(function, *args, **kwargs)
    )