code: def ping(self, t):
      """
      :type t: int
      :rtype: int
      """
      self.queue.append(t)
      while self.queue and self.queue[0] < t - 3000:
          self.queue.pop(0)
      return len(self.queue)
  
label_desc: Use image node_id 2 for calling the RecentCounter obj's underlying member method code with example usage: obj.ping(t) and returns: len