code: def timer():
      return time.time()
  
imports: from __future__ import absolute_import
  import csv
  import os
  import time
  from collections import OrderedDict
  from contextlib import contextmanager
  from importlib import import_module
  import numpy
  from nnabla.ext_utils import import_extension_module
  from .base import FunctionHookCallbackBase
label_desc: Use image node_id 4 for calling the CpuTimerCallback obj's underlying member method code with example usage: obj.timer() and returns: time