code: def serving_input_fn(self, hparams):
      
      video_input_frames = tf.placeholder(
          dtype=tf.float32,
          shape=[
              None, hparams.video_num_input_frames, self.frame_width,
              self.frame_height, self.num_channels
          ])
  
      # TODO(michalski): add support for passing input_action and input_reward.
      return tf.estimator.export.ServingInputReceiver(
          features={"inputs": video_input_frames},
          receiver_tensors=video_input_frames)
docs: For serving/predict, assume that only video frames are provided.