code: def test_reentrant(self):
      # In/grad data are random; these do not simulate the actually possible
      # cases.
      f = self.f
      # any function other than f: Exp is ok
      g = functions.math.identity.Identity()
  
      self.h.backward_preprocess(f, (self.x,), (self.gy,))
      self.h.forward_preprocess(g, (self.x,))
      self.h._memory_hook.used_bytes += 512
      self.h._memory_hook.acquired_bytes += 512
      self.h.forward_postprocess(g, (self.x,))
      self.h._memory_hook.used_bytes += 512
      self.h._memory_hook.acquired_bytes += 512
      self.h.backward_postprocess(f, (self.x,), (self.gy,))
  
      history = {f: (u, a, d) for (f, u, a, d) in self.h.call_history}
      self.assertEqual(len(history), 2)
      self.assertIn(f._impl_name, history)
      self.assertIn(g._impl_name, history)
      f_used_bytes, f_acquired_bytes, f_depth = history[f._impl_name]
      g_used_bytes, g_acquired_bytes, g_depth = history[g._impl_name]
      self.assertEqual(f_depth, 0)
      self.assertEqual(g_depth, 1)
      self.assertGreater(f_used_bytes, g_used_bytes)
      self.assertGreater(f_acquired_bytes, g_acquired_bytes)
  
imports: import unittest
  import numpy
  import six
  import chainer
  from chainer.backends import cuda
  from chainer import function_hooks
  from chainer import functions
  from chainer.functions.math import basic_math
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 7 for calling the TestCupyMemoryProfileHookToFunction obj's underlying member method code with example usage: obj.test_reentrant() without return types