code: def initialize(self, request, response):
      
      super(TaskQueueHandler, self).initialize(request, response)
  
      # Check request is from taskqueue.
      if "X-AppEngine-QueueName" not in self.request.headers:
        logging.error(self.request.headers)
        logging.error("Task queue handler received non-task queue request")
        self.response.set_status(
            403, message="Task queue handler received non-task queue request")
        return
  
      # Check task has not been retried too many times.
      if self.task_retry_count() + 1 > parameters.config.TASK_MAX_ATTEMPTS:
        logging.error(
            "Task %s has been attempted %s times. Dropping it permanently.",
            self.request.headers["X-AppEngine-TaskName"],
            self.task_retry_count() + 1)
        self._drop_gracefully()
        return
  
      try:
        self._preprocess()
        self._preprocess_success = True
      # pylint: disable=bare-except
      except:
        self._preprocess_success = False
        logging.error(
            "Preprocess task %s failed. Dropping it permanently.",
            self.request.headers["X-AppEngine-TaskName"])
        self._drop_gracefully()
docs: Initialize.
  
      1. call webapp init.
      2. check request is indeed from taskqueue.
      3. check the task has not been retried too many times.
      4. run handler specific processing logic.
      5. run error handling logic if precessing failed.
  
      Args:
        request: a webapp.Request instance.
        response: a webapp.Response instance.