def test_example(self):
     trans_dict = {
         'H': ['HO', 'OH'],
         'O': ['HH']
     }
     start = 'HOH'
     expect = 4
     # after 1 step:
     self.assertEqual(expect, get_num_combinations(start, trans_dict))
 def test_puzzle(self):
     trans_dict = parse_input(INPUT_TRANSFORMATION_STRING)
     result = get_num_combinations(INPUT_MOLECULE, trans_dict)
     print result