Stop the instances specified

        :type instance_ids: list
        :param instance_ids: A list of strings of the Instance IDs to stop

        :type force: bool
        :param force: Forces the instance to stop

        :rtype: list
        :return: A list of the instances stopped

def stop_instances(self, instance_ids=None, force=False):
        """
        Stop the instances specified

        :type instance_ids: list
        :param instance_ids: A list of strings of the Instance IDs to stop

        :type force: bool
        :param force: Forces the instance to stop

        :rtype: list
        :return: A list of the instances stopped
        """
        params = {}
        if force:
            params['Force'] = 'true'
        if instance_ids:
            self.build_list_params(params, instance_ids, 'InstanceId')
        return self.get_list('StopInstances', params,
                             [('item', Instance)], verb='POST')