code: def numpy_sub(a, b):
      return np.sub(a, b)
  
imports: from __future__ import absolute_import, print_function, division
  import unittest
  import theano
  import numpy
  from theano.gof import Op, Apply
  from theano import tensor, function, printing
  from theano.tests import unittest_tools
  import theano
  import numpy
  from theano.compile.ops import as_op
label_desc: Use image node_id 5 for calling a global function with example usage: numpy_sub(a, b) and returns: np