code: def testAllSumGrad(self):
      self._TestGradient(
          partial(_NcclAllReduce, nccl_ops.all_sum), lambda x, y: x + y
      )
  
imports: from functools import partial
  import numpy
  from tensorflow.python.framework import errors
  from tensorflow.python.framework import ops
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import gradients
  from tensorflow.python.ops import nccl_ops
  from tensorflow.python.platform import test
label_desc: Use image node_id 2 for calling the AllReduceTest obj's underlying member method code with example usage: obj.testAllSumGrad() without return types