Enables or disables layer 1 keepalive messages.

        :param state: boolean

def l1_keepalives(self, state):
        """
        Enables or disables layer 1 keepalive messages.

        :param state: boolean
        """

        self._l1_keepalives = state
        if state:
            log.info('IOU "{name}" [{id}]: has activated layer 1 keepalive messages'.format(name=self._name, id=self._id))
        else:
            log.info('IOU "{name}" [{id}]: has deactivated layer 1 keepalive messages'.format(name=self._name, id=self._id))