comefrom: <qiyuangong>141_Linked_List_Cycle_2.py
code: def hasCycle( head):
      dic = {}
      pos = head
      while pos is not None:
          try:
              dic[pos]
              return True
          except KeyError:
              dic[pos] = pos
          pos = pos.next
      return False
masked: def sample_funcname ( var_0 ) :
      var_1 = { }
      var_2 = var_0
      while var_2 is not None :
          try :
              var_1 [ var_2 ]
              return True
          except KeyError :
              var_1 [ var_2 ] = var_2
          var_2 = var_2.next
      return False
  