code: def _empty_slot(spec):
      shape = [s if s is not None else -1 for s in spec.shape.as_list()]
      shape = tf.convert_to_tensor(
          value=shape, dtype=tf.int64, name="shape"
      )
      return list_ops.empty_tensor_list(shape, spec.dtype)
  
file_path: agents/tf_agents/replay_buffers/episodic_table.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import tensorflow
  from tf_agents.utils import nest_utils
  from tensorflow.python.ops import list_ops
label_desc: Use image node_id 1 for calling a global function with example usage: _empty_slot(spec) and returns: list_ops