code: def pack_inputs(inputs):
      """Pack a list of `inputs` tensors to a tuple.
  
      Args:
        inputs: a list of tensors.
  
      Returns:
        a tuple of tensors. if any input is None, replace it with a special constant
        tensor.
      """
      inputs = tf.nest.flatten(inputs)
      outputs = []
      for x in inputs:
          if x is None:
              outputs.append(tf.constant(0, shape=[], dtype=tf.int32))
          else:
              outputs.append(x)
      return tuple(outputs)
  
file_path: autodist/examples/benchmark/utils/tf_utils.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import six
  import tensorflow
  from utils import activations
label_desc: Use image node_id 1 for calling a global function with example usage: pack_inputs(inputs) and returns: tuple