code: def _get_prev_next(self, urn):
          
          urn = URN(urn)
          subreference = None
          textId = urn.upTo(URN.NO_PASSAGE)
          if urn.reference is not None:
              subreference = str(urn.reference)
          previous, nextious = self.resolver.getSiblings(textId=textId, subreference=subreference)
          r = render_template(
              "cts/GetPrevNext.xml",
              prev_urn=previous,
              next_urn=nextious,
              urn=textId,
              request_urn=str(urn)
          )
          return r, 200, {"content-type": "application/xml"}
docs: Provisional route for GetPrevNext request
  
          :param urn: URN to filter the resource
          :param inv: Inventory Identifier
          :return: GetPrevNext response