@backtrack_onerror
def parse_link_label(self, reader: TextReader, document: Element, opener: Element=None, closer: Element=None) -> Tuple[(object, str)]:
    reader.step()
    refname = LinkLabelParser().parse(reader, document)
    if (refname == ''):
        refname = reader[opener['position']:closer['position']]
    target = self.lookup_target(document, refname)
    if target:
        destination = target.get('refuri')
        title = target.get('title')
        return (destination, title)
    else:
        return (LABEL_NOT_MATCHED, None)
@backtrack_onerror
def parse_link_label(self, reader: TextReader, document: Element, opener: Element=None, closer: Element=None) -> Tuple[(object, str)]:
    reader.step()
    refname = LinkLabelParser().parse(reader, document)
    if (refname == ):
        refname = reader[opener['position']:closer['position']]
    target = self.lookup_target(document, refname)
    if target:
        destination = target.get('refuri')
        title = target.get('title')
        return (destination, title)
    else:
        return (LABEL_NOT_MATCHED, None)