Returns a :class:`Signature` object based on the given `string`. If
        `option` is `True`, repetitions or optional patterns will not be
        allowed.

        If the `string` cannot be parsed, :exc:`InvalidSignature` is raised.

def from_string(cls, string, option=True):
        """
        Returns a :class:`Signature` object based on the given `string`. If
        `option` is `True`, repetitions or optional patterns will not be
        allowed.

        If the `string` cannot be parsed, :exc:`InvalidSignature` is raised.
        """
        return cls(_parse_signature(string, option=option))