Schedules a kill notification for this flow.

def ScheduleKillNotification(self):
    """Schedules a kill notification for this flow."""
    # Create a notification for the flow in the future that
    # indicates that this flow is in progess. We'll delete this
    # notification when we're done with processing completed
    # requests. If we're stuck for some reason, the notification
    # will be delivered later and the stuck flow will get
    # terminated.
    kill_timestamp = (rdfvalue.RDFDatetime().Now() + self.stuck_flows_timeout)
    with queue_manager.QueueManager(token=self.token) as manager:
      manager.QueueNotification(
          session_id=self.session_id,
          in_progress=True,
          timestamp=kill_timestamp)

    # kill_timestamp may get updated via flow.HeartBeat() calls, so we
    # have to store it in the context.
    self.context.kill_timestamp = kill_timestamp