code: def fan_out_fan_in():
      """The 'Pearlmutter test'"""
  
      def fun(x):
          for i in range(10**4):
              x = (x + x) / 2.0
          return np.sum(x)
  
      with tictoc():
          grad(fun)(1.0)
  
file_path: autograd/tests/profiling.py
imports: from __future__ import absolute_import
  from __future__ import print_function
  from builtins import range
  from autograd import grad
  import autograd.numpy
  import autograd.numpy.random
  from time import time
  from contextlib import contextmanager
label_desc: Use image node_id 2 for calling a global function with example usage: fan_out_fan_in() and returns: np