TFE_OpSetAttrInt(op.get(), "group_size", group_size);
  TFE_OpSetAttrInt(op.get(), "group_key", 0);
  TFE_OpSetAttrInt(op.get(), "instance_key", 0);
  const std::string merge_op("Add");
  TFE_OpSetAttrString(op.get(), "merge_op", merge_op.c_str(),
                      merge_op.length());
  const std::string final_op("Id");
  TFE_OpSetAttrString(op.get(), "final_op", final_op.c_str(),
                      final_op.length());

           "CollectiveReduce",
           {"x"},
           {{"T", DT_FLOAT},
            {"group_size", static_cast<int>(devices.size())},
            {"group_key", 0},
            {"instance_key", 0},
            {"merge_op", "Add"},
            {"final_op", "Id"},
            {"subdiv_offsets", std::vector<int>()}},
           /*dep=*/{"assert"}},
      });
  TF_ASSERT_OK(ContextFromInterface(unwrap(context.get()))

  TFE_OpSetAttrType(op, "T", TFE_TensorHandleDataType(in));
  TFE_OpSetAttrInt(op, "group_size", group_size);
  TFE_OpSetAttrInt(op, "group_key", 123);
  TFE_OpSetAttrInt(op, "instance_key", 456);
  TFE_OpSetAttrString(op, "merge_op", "Add", 3);
  TFE_OpSetAttrString(op, "final_op", "Id", 2);
  std::vector<int64_t> subdiv_offsets;
  TFE_OpSetAttrIntList(op, "subdiv_offsets", subdiv_offsets.data(),
                       subdiv_offsets.size());

  VerifyFDefOutputs(fdef, M({{"test_loop_exit"}}));
  VerifyFDefEdges(fdef,
                  {{"feed1", "test_loop/Enter:0"},
                   {"test_loop/Enter:output:0", "test_loop/Merge:0"},
                   {"test_loop/Merge:output:0", "test_loop/Switch:0"},
                   {"test_loop/Switch:output_false:0", "test_loop/Exit:0"},
                   {"test_loop/Exit:output:0", "test_loop_exit"}},
                  {}, false);