from tensorflow.python.framework import ops

    self.graph = None
    self.feed_tensors = None
    self.fetch_tensors = None

  def process(self, inputs):
    # Create a session for every worker only once. The session is not
    # pickleable, so it can't be created at the DoFn constructor.
    if not self.session:
      self.graph = ops.Graph()
      with self.graph.as_default():
        self.session = tf.Session()
        metagraph_def = loader.load(
            self.session, {self.meta_tag}, self.model_dir)
      signature_def = metagraph_def.signature_def[self.meta_signature]

      # inputs
