code: def testUseOutput(self):
      operators = [
          CreateOperator("UseOutput", "in", "hidden"),
          CreateOperator("UseOutput", "hidden", "out"),
          CreateOperator("Direct", "out", "sink"),
      ]
      desired_grad_operators = [
          CreateOperator("DirectGradient", "sink_grad", "out_grad"),
          CreateOperator(
              "UseOutputGradient", ["out", "out_grad"], "hidden_grad"
          ),
          CreateOperator(
              "UseOutputGradient", ["hidden", "hidden_grad"], "in_grad"
          ),
      ]
      gradients, _ = GradientRegistry.GetBackwardPass(
          operators, {"sink": "sink_grad"}
      )
      self.assertOperatorListEqual(gradients, desired_grad_operators)
  
imports: from hypothesis import given, settings
  import hypothesis.strategies
  import unittest
  from caffe2.proto import caffe2_pb2
  from caffe2.python import core, test_util, workspace
  from caffe2.python.core import CreateOperator, GradientRegistry, IR
  import numpy
label_desc: Use image node_id 8 for calling the TestGradientCalculation obj's underlying member method code with example usage: obj.testUseOutput() without return types