code: def set_thumbnail(self, **kwargs):
          
          self.thumbnail = {
              'url': kwargs.get('url'),
              'proxy_url': kwargs.get('proxy_url'),
              'height': kwargs.get('height'),
              'width': kwargs.get('width'),
          }
docs: set thumbnail of embed
          :keyword url: source url of thumbnail (only supports http(s) and attachments)
          :keyword proxy_url: a proxied thumbnail of the image
          :keyword height: height of thumbnail
          :keyword width: width of thumbnail