code: def _lazily_initialize(self):
      
      # TODO(nickfelt): remove on-demand imports once dep situation is fixed.
      import tensorflow.compat.v1 as tf
      with self._initialization_lock:
        if self._session:
          return
        graph = tf.Graph()
        with graph.as_default():
          self.initialize_graph()
        # Don't reserve GPU because libpng can't run on GPU.
        config = tf.ConfigProto(device_count={'GPU': 0})
        self._session = tf.Session(graph=graph, config=config)
docs: Initialize the graph and session, if this has not yet been done.