new_contents: # coding=UTF-8
  from __future__ import print_function, absolute_import, division
  import six
  import unittest
  
  from satella.coding import CallableGroup
  
  
  class TestCallableGroup(unittest.TestCase):
      def test_callable_group(self):
  
          a = {
              'a': False,
              'b': False
          }
  
          opF = lambda what: lambda: a.__setitem__(what, True)
  
          cg = CallableGroup()
  
          cg.add(opF('a'))
          cg.add(opF('b'))
  
          cg()
  
          self.assertTrue(all(a.values()))
  
  
subject: test for concurrent