Get the previous URN of a reference of the text

        :param reference: CtsReference from which to find siblings
        :type reference: Union[CtsReference, str]
        :return: (Previous CapitainsCtsPassage CtsReference,Next CapitainsCtsPassage CtsReference)

def getPrevNextUrn(self, reference):
        """ Get the previous URN of a reference of the text

        :param reference: CtsReference from which to find siblings
        :type reference: Union[CtsReference, str]
        :return: (Previous CapitainsCtsPassage CtsReference,Next CapitainsCtsPassage CtsReference)
        """
        _prev, _next = _SharedMethod.prevnext(
            self.retriever.getPrevNextUrn(
                urn="{}:{}".format(
                    str(
                        URN(
                            str(self.urn)).upTo(URN.NO_PASSAGE)
                    ),
                    str(reference)
                )
            )
        )
        return _prev, _next