public static function getAndAssertActiveBlock($type)
    {
        $active_block = static::getActive();
        $current = get_class($active_block->activeBlock());
        if ( !is_a($active_block->activeBlock(), $type)) {
            throw new Exception("Improperly nested block. Expected a $type, got a $current");
        }
        return $active_block;
    }