code: def set_response_content_type(self, response_content_types=None):
          '''Evaluate the content type for the response to a client ``request``.
  
          The method uses the :attr:`response_content_types` parameter of
          accepted content types and the content types accepted by the client
          ``request`` and figures out the best match.
          '''
          request_content_types = self.content_types
          if request_content_types:
              ct = request_content_types.best_match(response_content_types)
              if ct and '*' in ct:
                  ct = None
              if not ct and response_content_types:
                  raise HttpException(status=415, msg=request_content_types)
              self.response.content_type = cf set_response_content_type(self, response_content_types=None):
          '''Evaluate the content type for the response to a client ``request``.
  
          The method uses the :attr:`response_content_types` parameter of
          accepted content types and the content types accepted by the client
          ``request`` and figures out the best match.
          '''
          request_content_types = self.content_types
          if request_content_types:
              ct = request_content_types.best_match(response_content_types)
              if ct and '*' in ct:
                  ct = None
              if not ct and response_content_types:
                  raise HttpException(status=415, msg=request_content_types)
              self.response.content_type = ct
docs: Evaluate the content type for the response to a client ``request``.
  
          The method uses the :attr:`response_content_types` parameter of
          accepted content types and the content types accepted by the client
          ``request`` and figures out the best match.