code: def _allreduce(tensor, name=None):
      """An op which reduces an input tensor over all the Bluefog processes. The
      default reduction is a sum.
  
      The reduction operation is keyed by the name of the op. The tensor type and
      shape must be the same on all Bluefog processes for a given name. The reduction
      will not start until all processes are ready to send and receive the tensor.
  
      Returns:
        A tensor of the same shape and type as `tensor`, summed across all
        processes.
      """
      if name is None and not _executing_eagerly():
          name = "BluefogAllreduce_%s" % _normalize_name(tensor.name)
      return MPI_LIB.bluefog_allreduce(tensor, name=name)
  
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 4 for calling a global function with example usage: _allreduce(tensor, name) and returns: MPI_LIB