code: def is_tf_expression(x: Any) -> bool:
      """Check whether the input is a valid Tensorflow expression, i.e., Tensorflow Tensor, Variable, or Operation."""
      return isinstance(x, (tf.Tensor, tf.Variable, tf.Operation))
  
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 2 for calling a global function with example usage: is_tf_expression(x) and returns: isinstance