# Buggy code
def __call__(
    self, name: Optional[str] = None, key: Optional[Callable] = None, **kwargs
) -> Any:
    """Override standard call.

    This magic method override standard call so it's take any string which
    represents name of the any method of any supported data provider
    and the ``**kwargs`` of this method.

    ..note:: Some data providers have methods with the same name and
    in such cases, you can explicitly define that the method belongs to
    data-provider ``name='provider.name'``.

    You can apply a *key function* to result returned by the method,
    to do it, just pass parameter **key** with a callable object which
    returns final result.

    :param name: Name of the method.
    :param key: A key function (or other callable object)
        which will be applied to result.
    :param kwargs: Kwargs of method.
    :return: Value which represented by method.
    :raises ValueError: if provider is not
        supported or if field is not defined.
    """
    if name is None:
        raise UndefinedField()

    def tail_parser(tails: str, obj: Any) -> Any:
        """Return method from end of tail.

        :param tails: Tail string
        :param obj: Search tail from this object
        :return last tailed method
        """
        first, second = tails.split(".", 1)
        if hasattr(obj, first):
            attr = getattr(obj, first)
            if "." in second:
                return tail_parser(attr, second)
            else:
                return getattr(attr, second)

    try:
        if name not in self._table:
            if "." not in name:
                for provider in dir(self._gen):
                    provider = getattr(self._gen, provider)
                    if name in dir(provider):
                        self._table[name] = getattr(provider, name)
            else:
                self._table[name] = tail_parser(name, self._gen)

        result = self._table[name](**kwargs)
        if key and callable(key):
            return key(result)
        return result
    except Exception:
        raise UnsupportedField(name)


# Traceback (KeyError)
from mimesis.schema import Field, Schema
_ = Field('en')
_('choice', items=[1,2,3])
Traceback (most recent call last):
File "C:\dev\fakemimesis\.pyenv\lib\site-packages\mimesis\schema.py", line 100, in __call__
result = self._table[name](**kwargs)
KeyError: 'choice'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "<pyshell#24>", line 1, in <module>
_('choice', items=[1,2,3])
File "C:\dev\fakemimesis\.pyenv\lib\site-packages\mimesis\schema.py", line 105, in __call__
raise UnsupportedField(name)
mimesis.exceptions.UnsupportedField: Field «choice» is not supported.


# Fixed code
def __call__(
    self, name: Optional[str] = None, key: Optional[Callable] = None, **kwargs
) -> Any:
    """Override standard call.

    This magic method override standard call so it's take any string which
    represents name of the any method of any supported data provider
    and the ``**kwargs`` of this method.

    ..note:: Some data providers have methods with the same name and
    in such cases, you can explicitly define that the method belongs to
    data-provider ``name='provider.name'``.

    You can apply a *key function* to result returned by the method,
    to do it, just pass parameter **key** with a callable object which
    returns final result.

    :param name: Name of the method.
    :param key: A key function (or other callable object)
        which will be applied to result.
    :param kwargs: Kwargs of method.
    :return: Value which represented by method.
    :raises ValueError: if provider is not
        supported or if field is not defined.
    """
    if name is None:
        raise UndefinedField()

    def tail_parser(tails: str, obj: Any) -> Any:
        """Return method from end of tail.

        :param tails: Tail string
        :param obj: Search tail from this object
        :return last tailed method
        """
        provider_name, method_name = tails.split(".", 1)

        if "." in method_name:
            raise UnacceptableField()

        attr = getattr(obj, provider_name)
        if attr is not None:
            return getattr(attr, method_name)

    try:
        if name not in self._table:
            if "." not in name:
                # Fix https://github.com/lk-geimfari/mimesis/issues/619
                if name == self._gen.choice.Meta.name:
                    self._table[name] = self._gen.choice
                else:
                    for provider in dir(self._gen):
                        provider = getattr(self._gen, provider)
                        if name in dir(provider):
                            self._table[name] = getattr(provider, name)
            else:
                self._table[name] = tail_parser(name, self._gen)

        result = self._table[name](**kwargs)
        if key and callable(key):
            return key(result)
        return result
    except KeyError:
        raise UnsupportedField(name)