code: def test_merges_down(self):
      # o     x --> o
      # |           ^
      #  \_________/
      def fn(v, w, x, y):
          a = v * w
          b = torch.ones(int(y))
          c = b * a
          return a, c
  
      graph = self._perform_ad_subgraph_slicing(fn, 1, 1, 1, 1)
  
      num_nodes = 4 if GRAPH_EXECUTOR == ProfilingMode.PROFILING else 3
      # add moved down
      g_str = str(graph)
      FileCheck().check_not("aten::add").run(
          g_str[0 : g_str.find("return")]
      )
      self.assertGraphContainsExactly(
          graph, "prim::DifferentiableGraph", 1
      )
  
imports: import os
  import sys
  import unittest
  from torch.testing._internal.common_utils import GRAPH_EXECUTOR, ProfilingMode, num_profiled_runs, enable_profiling_mode_for_profiling_tests
  from torch.testing._internal.common_jit import check_against_reference
  import torch
  from torch.testing._internal.jit_utils import JitTestCase, disable_autodiff_subgraph_inlining
  from torch.testing import FileCheck
  from typing import List, Tuple, Optional
label_desc: Use image node_id 18 for calling the TestAutodiffSubgraphSlicing obj's underlying member method code with example usage: obj.test_merges_down() and returns: a,  c