@classmethod
    def mutate_and_get_payload(cls, input, context, info):
        user = context.user
        old_password = input.get('old_password')
        new_password = input.get('new_password')

        if user.has_usable_password():
            if not user.check_password(old_password):
                raise ResponseError(
                    "Invalid Password",
                    code='invalid_old_password')
        # ...