In this kata, you will make a function that converts between `camelCase`, `snake_case`, and `kebab-case`.

You must write a function that changes to a given case. It must be able to handle all three case types:

```python
py> change_case("snakeCase", "snake")
"snake_case"
py> change_case("some-lisp-name", "camel")
"someLispName"
py> change_case("map_to_all", "kebab")
"map-to-all"
py> change_case("doHTMLRequest", "kebab")
"do-h-t-m-l-request"
py> change_case("invalid-inPut_bad", "kebab")
None
py> change_case("valid-input", "huh???")
None
py> change_case("", "camel")
""
```

Your function must deal with invalid input as shown, though it will only be passed strings. Furthermore, all valid identifiers will be lowercase except when necessary, in other words on word boundaries in `camelCase`.

_**(Any translations would be greatly appreciated!)**_

```python

USER_FILENAME = "<user_code>"
import sys, json, builtins
import math, heapq, bisect, itertools, functools, collections, statistics, fractions, decimal, operator, array, random, re, string, os, pathlib
try:
    import resource as _res
except Exception:
    _res = None
from collections import Counter, defaultdict, deque, OrderedDict
from functools import lru_cache, reduce
from itertools import accumulate, permutations, combinations, product
from math import gcd, ceil, floor, sqrt
from decimal import Decimal
try:
    from typing import *
except Exception:
    pass
try:
    sys.setrecursionlimit(1_000_000)
except Exception:
    pass
try:
    import site as _site
    try:
        _sys_sites = _site.getsitepackages() if hasattr(_site, "getsitepackages") else []
        for _p in _sys_sites:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
    try:
        _usp = _site.getusersitepackages()
        if isinstance(_usp, str):
            _usp = [_usp]
        for _p in _usp:
            if _p and _p not in sys.path:
                sys.path.append(_p)
    except Exception:
        pass
except Exception:
    pass

def _disabled_input(*args, **kwargs):
    raise RuntimeError("input() is disabled in callable mode")
builtins.input = _disabled_input

ns = {"__name__": "__judge__"}  # prevent if __name__ == "__main__" blocks
for _k, _v in list(globals().items()):
    if not _k.startswith("_"):
        ns[_k] = _v
_CODE = 'import re\n\ndef is_snake_case(identifier):\n    return bool( re.fullmatch(r\'[a-z_]+\', identifier) )\n\ndef is_camel_case(identifier):\n    return bool(re.fullmatch(r\'([a-z]+[A-Z])+[a-z]*\', identifier))\n\ndef is_kebab_case(identifier):\n    return bool(re.fullmatch(r\'[a-z]*-?\', identifier))\n  \ndef is_mixed_case(identifier):\n    if "-" in identifier and "_" in identifier:\n        return True\n    elif "-" in identifier and [c for c in identifier if c.isupper()]:\n        return True\n    elif "_" in identifier and [c for c in identifier if c.isupper()]:\n        return True\n                \ndef change_case(identifier, targetCase):\n    # if identifier is empty\n    if not identifier:\n        return ""\n    \n    # if targetCase is invalid\n    elif targetCase not in [\'kebab\', \'camel\', \'snake\']:\n        return None\n    \n    # if identifier is mixed case\n    elif is_mixed_case(identifier):\n        return None\n    \n    # change case to snake case\n    elif targetCase == "snake" and not is_snake_case(identifier):\n        split = [char for char in re.split(r\'([A-Z]|-)\', identifier) if char]\n        for i, char in enumerate(split):\n            if char.isupper():\n                split[i] = \'_\' + char.lower()\n            elif char == "-":\n                split[i] = "_"\n        return \'\'.join(split)\n    \n    # change case to camel case\n    elif targetCase == "camel" and not is_camel_case(identifier):    \n        split = re.split(r\'[_-]\', identifier)\n        return split[0] + \'\'.join(word.title() for word in split[1:])\n        \n    # change case to kebab case\n    elif targetCase == "kebab" and not is_kebab_case(identifier):\n        split = re.split(r\'([A-Z]|_)\', identifier)\n        kebab = split[0]\n        for i, word in enumerate(split[1:]):\n            if not word or word == "_":\n                kebab += "-"\n            elif word.isupper():\n                if kebab[-1] == "-":                    \n                    kebab += word.lower()\n                else:\n                    kebab += \'-\' + word.lower()\n            else:\n                kebab += word.lower()\n        return kebab\n    \n    # identifier and targetCase already match\n    else:\n        return identifier'
_co = compile(_CODE, USER_FILENAME, "exec")
exec(_co, ns, ns)

_target = None
_fn_name = 'change_case'
if _fn_name:
    if "Solution" in ns:
        try:
            _obj = ns["Solution"]()
            if hasattr(_obj, _fn_name):
                _target = getattr(_obj, _fn_name)
        except Exception:
            _target = None
    if _target is None and _fn_name in ns and callable(ns[_fn_name]):
        _target = ns[_fn_name]
# Fallback: if there's exactly one user-defined function, use it
if _target is None:
    _cands = [v for k, v in ns.items() if callable(v) and getattr(v, "__module__", "") in ("__judge__", "__main__")]
    _user_funcs = [c for c in _cands if getattr(c, "__name__", "").startswith("_") is False]
    if len(_user_funcs) == 1:
        _target = _user_funcs[0]
if _target is None:
    raise RuntimeError(f"Could not resolve callable '{_fn_name}'")

_raw = sys.stdin.read().strip()
if _raw:
    _parsed = json.loads(_raw)
    if isinstance(_parsed, dict):
        _kwargs = _parsed.get("kwargs", {})
        _args = _parsed.get("args", [])
    else:
        _args, _kwargs = _parsed, {}
else:
    _args, _kwargs = [], {}
if not isinstance(_args, (list, tuple)):
    _args = [_args]
_res = _target(*_args, **_kwargs)
try:
    sys.stdout.write(repr(_res) + "\n")
except Exception:
    pass

```

Measured memory_bytes: 36952