Retrieve the siblings of a textual node

        :param textId: CtsTextMetadata Identifier
        :type textId: str
        :param level: Depth for retrieval
        :type level: int
        :param subreference: CapitainsCtsPassage CtsReference
        :type subreference: str
        :return: List of references
        :rtype: [str]

def getReffs(self, textId, level=1, subreference=None):
        """ Retrieve the siblings of a textual node

        :param textId: CtsTextMetadata Identifier
        :type textId: str
        :param level: Depth for retrieval
        :type level: int
        :param subreference: CapitainsCtsPassage CtsReference
        :type subreference: str
        :return: List of references
        :rtype: [str]
        """
        passage, inventory = self.__getText__(textId)
        if subreference:
            passage = passage.getTextualNode(subreference)
        return passage.getReffs(level=level, subreference=subreference)