code: def _allreduce_grad(op, grad):
      """Gradient for allreduce 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.
      """
      return _allreduce(grad)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import re
  import tensorflow
  from tensorflow.python.framework import load_library
  from tensorflow.python.framework import ops
  from tensorflow.python.platform import resource_loader
  from bluefog.common.basics import BlueFogBasics
  from bluefog.common.util import get_ext_suffix
  from bluefog.tensorflow.util import _executing_eagerly
label_desc: Use image node_id 5 for calling a global function with example usage: _allreduce_grad(op, grad) and returns: _allreduce