code: def get(self, media_id):
          
          def _processor(res):
              if isinstance(res, dict):
                  if 'news_item' in res:
                      # 图文素材
                      return res['news_item']
              return res
  
          res = self._post(
              'material/get_material',
              data={
                  'media_id': media_id
              },
              result_processor=_processor
          )
          return res
docs: 获取永久素材
          详情请参考
          http://mp.weixin.qq.com/wiki/4/b3546879f07623cb30df9ca0e420a5d0.html
  
          :param media_id: 素材的 media_id
          :return: 图文素材返回图文列表，其它类型为素材的内容