Returns the path for storing variables checkpoints.

def get_variables_path(export_dir):
  """Returns the path for storing variables checkpoints."""
  return os.path.join(
      tf.compat.as_bytes(export_dir),
      tf.compat.as_bytes(tf_v1.saved_model.constants.VARIABLES_DIRECTORY),
      tf.compat.as_bytes(tf_v1.saved_model.constants.VARIABLES_FILENAME))