code: def manhattan(a, b):
      a2 = a.copy()
      b2 = b.copy()
  
      ans = 0
      keys = set(a.keys()).union(set(b.keys()))
      for k in keys:
          a2.setdefault(k, 0)
          b2.setdefault(k, 0)
          ans += abs(a2[k] - b2[k])
      return ans
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import copy
  import unittest
  import numpy
  import turicreate
  from turicreate.toolkits._main import ToolkitError
  from collections import Counter
  import sys
label_desc: Use image node_id 7 for calling a global function with example usage: manhattan(a, b) and returns: ans