Split state string.

        Parameters
        ----------
        state : `str`

        Returns
        -------
        `list` of `str`

def split_state(self, state):
        """Split state string.

        Parameters
        ----------
        state : `str`

        Returns
        -------
        `list` of `str`
        """
        if self.state_separator:
            return state.split(self.state_separator)
        return list(state)