code: def build_fake_controller(cell):
      """Create a scalar variable to track the timestep.
  
      Args:
        cell: The NeuralStackCell to add the variable to.
      """
      cell.current_step = cell.add_variable(
          "current_step",
          [],
          initializer=tf.constant_initializer(-1),
          dtype=tf.int32,
          trainable=False,
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import mock
  import numpy
  from tensor2tensor.layers import modalities
  from tensor2tensor.models.research import neural_stack
  from tensor2tensor.utils import contrib
  import tensorflow.compat.v1
label_desc: Use image node_id 1 for calling a global function with example usage: build_fake_controller(cell) without return types