def set_thumbnail(self, *, url):
self._thumbnail = {<EOL>'<STR_LIT:url>': str(url)<EOL>}<EOL>return self<EOL>
Sets the thumbnail for the embed content.

        This function returns the class instance to allow for fluent-style
        chaining.

        Parameters
        -----------
        url: :class:`str`
            The source URL for the thumbnail. Only HTTP(S) is supported.