code: def assert_tf_initialized():
      """Check that TensorFlow session has been initialized."""
      if tf.get_default_session() is None:
          raise RuntimeError(
              "No default TensorFlow session found. Please call dnnlib.tflib.init_tf()."
          )
  
imports: import os
  import numpy
  import tensorflow
  import logging
  import tensorflow.contrib
  from typing import Any, Iterable, List, Union
label_desc: Use image node_id 13 for calling a global function with example usage: assert_tf_initialized() without return types