class_docstr: An autograd function that performs push_pull on a tensor.
class_docstr_tok: ["An","autograd","function","that","performs","push_pull","on","a","tensor","."]
code: def backward(ctx, grad_output):
      return (
          push_pull(
              grad_output,
              ctx.average,
              ctx.name,
              ctx.version,
              ctx.priority,
          ),
          None,
          None,
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from distutils.version import LooseVersion
  import torch
  from byteps.torch import c_lib
  from byteps.common import BytePSBasics
  from byteps.torch.compression import Compression
label_desc: Use image node_id 2 for calling the BytePSPushPull obj's underlying member method code with example usage: obj.backward(ctx, grad_output) and returns: push_pull,  None,  None