code: def _request(self, endpoint, data, auth=None):
          
          url = '{}/{}'.format(self.base_url, endpoint)
          response = requests.post(url, data, auth=auth)
          return self._handle_response(response)
docs: Make HTTP POST request to an API endpoint.
          :param str endpoint: API endpoint's relative URL, eg. `/account`.
          :param dict data: POST request data.
          :param tuple auth: HTTP basic auth credentials.
          :return: A dictionary or a string with response data.