docs: def siblingsId(self) -> Tuple[CtsReference, CtsReference]:
          """ Siblings Identifiers of the passage
  
          :rtype: (str, str)
          """
          self._raise_depth()
  
          if not self._text:
              raise MissingAttribute("CapitainsCtsPassage was initiated without CtsTextMetadata object")
          if self._prev_next:
              return self._prev_next
  
          document_references = self._text.getReffs(level=self.depth)
  
          if self.reference.is_range():
              start, end = self.reference.start, self.reference.end
              range_length = len(self.getReffs(level=0))
          else:
              start = end = self.reference.start
              range_length = 1
  
          start = document_references.index(start)
          end = document_references.index(end)
  
          if start == 0:
              # If the passage is already at the beginning
              _prev = None
          elif start - range_length < 0:
              if start == end:
                  _prev = document_references[0]
              else:
                  _prev = "{}-{}".format(document_references[0], document_references[start-1])
          else:
              if start == end:
                  _prev = document_references[start-1]
              else:
                  _prev = "{}-{}".format(document_references[start-range_length], document_references[start-1])
  
          if start + 1 == len(document_references) or end + 1 == len(document_references):
              # If the passage is already at the end
              _next = None
          elif end + range_length > len(document_references):
              if start == end:
                  _next = document_references[-1]
              else:
                  _next = "{}-{}".format(document_references[end+1], document_references[-1])
          else:
              if start == end:
                  _next = document_references[end+1]
              else:
                  _next = "{}-{}".format(document_references[end+1], document_references[end + range_length])
  
          self._prev_next = (CtsReference(_prev), CtsReference(_next))
          return self._prev_next