Handle a client disconnect.

def _handle_disconnect(self, sid, namespace):
        """Handle a client disconnect."""
        namespace = namespace or '/'
        if namespace == '/':
            namespace_list = list(self.manager.get_namespaces())
        else:
            namespace_list = [namespace]
        for n in namespace_list:
            if n != '/' and self.manager.is_connected(sid, n):
                self._trigger_event('disconnect', n, sid)
                self.manager.disconnect(sid, n)
        if namespace == '/' and self.manager.is_connected(sid, namespace):
            self._trigger_event('disconnect', '/', sid)
            self.manager.disconnect(sid, '/')