Given a passageId matches a citation level

        :param passageId: A passage to match
        :return:

def match(self, passageId):
        """ Given a passageId matches a citation level

        :param passageId: A passage to match
        :return:
        """
        if not isinstance(passageId, CtsReference):
            passageId = CtsReference(passageId)

        if self.is_root():
            return self[passageId.depth-1]
        return self.root.match(passageId)