def fetch_access_token(self):
expires_in = <NUM_LIT><EOL>result = self.component.refresh_authorizer_token(<EOL>self.appid, self.refresh_token)<EOL>if '<STR_LIT>' in result:<EOL><INDENT>expires_in = result['<STR_LIT>']<EOL><DEDENT>self.session.set(<EOL>self.access_token_key,<EOL>result['<STR_LIT>'],<EOL>expires_in<EOL>)<EOL>self.expires_at = int(time.time()) + expires_in<EOL>return result<EOL>
获取 access token
详情请参考 https://open.weixin.qq.com/cgi-bin/showdocument?action=dir_list\
&t=resource/res_list&verify=1&id=open1419318587&token=&lang=zh_CN

这是内部刷新机制。请不要完全依赖！
因为有可能在缓存期间没有对此公众号的操作，造成refresh_token失效。

:return: 返回的 JSON 数据包