code: def getSiblings(self, textId, subreference):
          
          text = CtsText(
              urn=textId,
              retriever=self.endpoint
          )
          return text.getPrevNextUrn(subreference)
docs: Retrieve the siblings of a textual node
  
          :param textId: CtsTextMetadata Identifier
          :type textId: str
          :param subreference: CapitainsCtsPassage Reference
          :type subreference: str
          :return: Tuple of references
          :rtype: (str, str)