def close(self):
if self._closed:<EOL><INDENT>return<EOL><DEDENT>self._closed = True<EOL>if self._active_js is not None:<EOL><INDENT>self._active_js.cancel()<EOL><DEDENT>for js in self._js_queue:<EOL><INDENT>js.cancel()<EOL><DEDENT>
Closes the job manager. No more jobs will be assigned, no more job sets
will be added, and any queued or active job sets will be cancelled.