def _complete_url(self, url_part, registration_prefix):
        parts = {
            'b': registration_prefix,
            'a': self.prefix,
            'e': url_part
        }
        return ''.join(parts[key] for key in self.url_part_order if parts[key])
This method is used to defer the construction of the final url in
dataset/ETHPy150Open flask-restful/flask-restful/flask_restful/__init__.py/Api._complete_url