docs: 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 Reference
          :type subreference: str
          :return: List of references
          :rtype: [str]
          """
          depth = level
          if subreference:
              textId = "{}:{}".format(textId, subreference)
          if subreference:
              if isinstance(subreference, CtsReference):
                  depth += subreference.depth
              else:
                  depth += (CtsReference(subreference)).depth
          if level:
              level = max(depth, level)
          return self.getValidReff(urn=textId, level=level)