human
Solve the following python programming problem given the following code:
def _sort_footnotes(self, text) : 
    'Because _do_links is not applied to the text in text flow order, footnotes are not generated in proper order, we have to sort them before _add_footnotes.
        ' 
    _footnote_tag_re = re.compile ('<sup class="footnote-ref" id="fnref-(.+)"><a href="#fn-\\1">(\\d+)</a></sup>') 
    self.footnote_ids = [] 
    def _repl(match) : 
        id = match.group (1) 
        num = match.group (2) 
        if (id in self.footnotes) : 
            self.footnote_ids.append (id) 
            return ((match.string [match.start (0) : match.start (2)] + str (len (self.footnote_ids))) + match.string [match.end (2) : match.end (0)]) 
else : 
            return match.string [match.start () : match.end ()] 
return _footnote_tag_re.sub (text, text) 

    
    

    Fix the buggy line: return _footnote_tag_re.sub (text, text)
assistant
#Here is Python program to fix the buggy line: return _footnote_tag_re.

return _footnote_tag_re.sub (def _repl(, text)