code: def _send_success_response(self, response, start_response):
      
      headers = [('Content-Type', 'application/json; charset=UTF-8')]
      return util.send_wsgi_response('200 OK', headers, response, start_response)
docs: Sends an HTTP 200 json success response.
  
      This calls start_response and returns the response body.
  
      Args:
        response: A string containing the response body to return.
        start_response: A function with semantics defined in PEP-333.
  
      Returns:
        A string, the response body.