Added the ability to give directly a callable object to the on_disconnect callback.

        else:

            pass # Malformed messages are note processed

    def shutdown(self, callback_name=None):

    def shutdown(self, callback=None):

        '''

        Shutdown this connection.

        :param callback_name: Name of the callback to call on the handler

        :type callback_name: :class:`str` or None

        :param callback: Name of the callback to call on the handler or a

            callable to call when the connection is shutdown.

        :type callback: :class:`str` or callable or None

        '''

        self._sock.close()

        if callback_name is not None and self._handler is not None:

        if callback is not None and not callable(callback):

            if self._handler is not None:

                try:

                func = self._handler[callback_name]

                    callback = self._handler[callback]

                except KeyError:

                pass

                    callback = None

            else:

                func(self)

                callback = None

        if callback is not None:

            try:

                callback(self)

            except Exception as err:

                logging.error('Error while execution of shutdown '

                              'callback: %s' % err)

    def clean_call(self, msg_id):

        '''