human
Solve the following python programming problem given the following code:
def _real_extract(self, url) : 
    mobj = re.match (self._VALID_URL, url) 
    movie = mobj.group ('movie') 
    uploader_id = mobj.group ('company') 
    playlist_url = compat_urlparse.urljoin (url, 'includes/playlists/itunes.inc') 
    def fix_html(s) : 
        s = re.sub ('(?s)<script[^<]*?>.*?</script>', '', s) 
        s = re.sub ('<img ([^<]*?)>', '<img \\1/>', s) 
        def _clean_json(m) : 
            return ('iTunes.playURL(%s);' % m.group (1).replace ("'", '&#39;')) 
s = re.sub (self._JSON_RE, _clean_json, s) 
        s = ('<html>%s</html>' % s) 
        return s 
doc = self._download_xml (playlist_url, movie, transform_source = fix_html) 
    playlist = [] 
    for li in doc.findall ('./div/ul/li') : 
        on_click = li.find ('.//a').attrib ['onClick'] 
        trailer_info_json = self._search_regex (self._JSON_RE, on_click, 'trailer info') 
        trailer_info = json.loads (trailer_info_json) 
        title = trailer_info ['title'] 
        video_id = ((movie + '-') + re.sub ('[^a-zA-Z0-9]', '', title).lower ()) 
        thumbnail = li.find ('.//img').attrib ['src'] 
        upload_date = trailer_info ['posted'].replace ('-', '') 
        runtime = trailer_info ['runtime'] 
        m = re.search ('(?P<minutes>[0-9]+):(?P<seconds>[0-9]{1,2})', runtime) 
        duration = None 
        if m : 
            duration = ((60 * int (m.group ('minutes'))) + int (m.group ('seconds'))) 
first_url = mobj ['url'] 
        trailer_id = first_url.split ('/') [(- 1)].rpartition ('_') [0].lower () 
        settings_json_url = compat_urlparse.urljoin (url, ('includes/settings/%s.json' % trailer_id)) 
        settings = self._download_json (settings_json_url, trailer_id, 'Downloading settings json') 
        formats = [] 
        for format in settings ['metadata'] ['sizes'] : 
            format_url = re.sub ('_(\\d*p.mov)', '_h\\1', format ['src']) 
            formats.append ({ 
                'url' : format_url, 
                'format' : format ['type'], 
                'width' : int_or_none...

    
    

    Fix the buggy line: first_url = mobj ['url']
assistant
#Here is Python program to find ('.

first_url = trailer_info ['url']