def complement(self, alphabet):
        """
        Returns the complement of DFA
        Args:
            alphabet (list): The input alphabet
        Returns:
            None
        """
        self._addsink(alphabet)
        for state in self.automaton.states():
            if self.automaton.final(state) == fst.Weight.One(self.automaton.weight_type()):
                self.automaton.set_final(state, fst.Weight.Zero(self.automaton.weight_type()))
            else:
                self.automaton.set_final(state, fst.Weight.One(self.automaton.weight_type()))