code: def unify_walk(o, n, U):
      r"""
      OrV(list1) == NV(list2) == OrV(list1 \ list2)
  
      """
      opt = [x for x in o.options if x not in n.not_options]
      if not opt:
          return False
      elif len(opt) == 1:
          v = BoundVariable("?", opt[0])
      else:
          v = OrVariable("?", opt)
      return U.merge(v, o, n)
  
imports: from __future__ import absolute_import, print_function, division
  from copy import copy
  from functools import partial
  from theano.gof.utils import ANY_TYPE, comm_guard, FALL_THROUGH, iteritems
label_desc: Use image node_id 11 for calling a global function with example usage: unify_walk(o, n, U) and returns: U, False