Retrieve the siblings of a textual node

        :param textId: CtsTextMetadata Identifier
        :type textId: str
        :param subreference: CapitainsCtsPassage CtsReference
        :type subreference: str
        :return: Tuple of references
        :rtype: (str, str)

def getSiblings(self, textId, subreference: CtsReference):
        """ Retrieve the siblings of a textual node

        :param textId: CtsTextMetadata Identifier
        :type textId: str
        :param subreference: CapitainsCtsPassage CtsReference
        :type subreference: str
        :return: Tuple of references
        :rtype: (str, str)
        """
        text, inventory = self.__getText__(textId)
        if not isinstance(subreference, CtsReference):
            subreference = CtsReference(subreference)
        passage = text.getTextualNode(subreference)
        return passage.siblingsId