Helper method to both parse and validate phone and its hash.

def _parse_phone_and_hash(self, phone, phone_hash):
        """
        Helper method to both parse and validate phone and its hash.
        """
        phone = utils.parse_phone(phone) or self._phone
        if not phone:
            raise ValueError(
                'Please make sure to call send_code_request first.'
            )

        phone_hash = phone_hash or self._phone_code_hash.get(phone, None)
        if not phone_hash:
            raise ValueError('You also need to provide a phone_code_hash.')

        return phone, phone_hash