A decorator that marks a function as a listener.

        This is the cog equivalent of :meth:`.Bot.listen`.

        Parameters
        ------------
        name: :class:`str`
            The name of the event being listened to. If not provided, it
            defaults to the function's name.

        Raises
        --------
        TypeError
            The function is not a coroutine function or a string was not passed as
            the name.

def listener(cls, name=None):
        """A decorator that marks a function as a listener.

        This is the cog equivalent of :meth:`.Bot.listen`.

        Parameters
        ------------
        name: :class:`str`
            The name of the event being listened to. If not provided, it
            defaults to the function's name.

        Raises
        --------
        TypeError
            The function is not a coroutine function or a string was not passed as
            the name.
        """

        if name is not None and not isinstance(name, str):
            raise TypeError('Cog.listener expected str but received {0.__class__.__name__!r} instead.'.format(name))

        def decorator(func):
            actual = func
            if isinstance(actual, staticmethod):
                actual = actual.__func__
            if not inspect.iscoroutinefunction(actual):
                raise TypeError('Listener function must be a coroutine function.')
            actual.__cog_listener__ = True
            to_assign = name or actual.__name__
            try:
                actual.__cog_listener_names__.append(to_assign)
            except AttributeError:
                actual.__cog_listener_names__ = [to_assign]
            # we have to return `func` instead of `actual` because
            # we need the type to be `staticmethod` for the metaclass
            # to pick it up but the metaclass unfurls the function and
            # thus the assignments need to be on the actual function
            return func
        return decorator