code: def GetHTTPHeaders(self):
      
      http_headers = self._adwords_client.oauth2_client.CreateHttpHeader()
      if self.enable_compression:
        http_headers['accept-encoding'] = 'gzip'
  
      http_headers.update(self.custom_http_headers)
  
      return http_headers
docs: Returns the HTTP headers required for request authorization.
  
      Returns:
        A dictionary containing the required headers.