code: def check_forward(self, x):
      self.f.apply((chainer.Variable(x),))
      assert len(self.h.call_history) == 1
      check_history(
          self,
          self.h.call_history[0],
          functions.math.exponential.Exp,
          float,
      )
  
imports: import os
  import time
  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 2 for calling the TestTimerHookToFunction obj's underlying member method code with example usage: obj.check_forward(x) without return types