code: def _broadcast_grad(op, grad):
      """Gradient for broadcast op.
      Args:
        op: An operation.
        grad: `Tensor` gradient with respect to the output of the op.
      Returns:
        The gradient with respect to the input of the op.
      """
      root_rank = op.get_attr("root_rank")
      grad_reduced = _push_pull(grad)
      if rank() != root_rank:
          return grad_reduced * 0
      return grad_reduced
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import re
  import os
  import ctypes
  from enum import Enum
  import random
  import string
  import warnings
  from tensorflow.python.framework import load_library
  from tensorflow.python.framework import ops
  from tensorflow.python.platform import resource_loader
  from byteps.common import get_ext_suffix
  from byteps.common import BytePSBasics
  from byteps.tensorflow.util import _executing_eagerly
  import tensorflow
label_desc: Use image node_id 8 for calling a global function with example usage: _broadcast_grad(op, grad) and returns: grad_reduced, unknown