@property<EOL><INDENT>@check_soup('<STR_LIT>')<EOL>def photo_url(self):<DEDENT>
img = self.soup.find('<STR_LIT:a>', id='<STR_LIT>').img['<STR_LIT:src>']<EOL>return img.replace('<STR_LIT>', '<STR_LIT>')<EOL>
获取话题头像图片地址.

        :return: 话题头像url
        :rtype: str