code: def _copy(self):
          
          table = {}
          for existingState, existingOutputs in self.table.items():
              table[existingState] = {}
              for (existingInput, existingTransition) in existingOutputs.items():
                  table[existingState][existingInput] = existingTransition
          return TransitionTable(table)
docs: Create a new L{TransitionTable} just like this one using a copy of the
          underlying transition table.
  
          @rtype: L{TransitionTable}