code: def add_directive(self, directive):
          # type: (Directive) -> 'ResponseFactory'
          
          if self.response.directives is None:
              self.response.directives = []
  
          if (directive is not None and
                  directive.object_type == "VideoApp.Launch"):
              self.response.should_end_session = None
          self.response.directives.append(directive)
          return self
docs: Adds directive to response.
  
          :param directive: the directive sent back to Alexa device.
          :type directive: ask_sdk_model.directive.Directive
          :return: response factory with partial response being built and
              access from self.response.
          :rtype: ResponseFactory