Get initial states from input string.

        Parameters
        ----------
        string : `str` or `None`
        backward : `bool`

        Returns
        -------
        `tuple` of `str`

def get_cont_state(self, string, backward=False):
        """Get initial states from input string.

        Parameters
        ----------
        string : `str` or `None`
        backward : `bool`

        Returns
        -------
        `tuple` of `str`
        """
        if string is None:
            return ()
        for _ in self.parser(self.scanner(string, True), True):
            if backward and len(self.parser.state[0]):
                break
        state = tuple(self.parser.state)
        self.scanner.reset()
        self.parser.reset()
        return state