public function echoSlot($key)
    {
        if (isset($this->_slots[$key])) {
            if (is_string($this->_slots[$key])) {
                echo $this->_slots[$key];
            } else {
                call_user_func($this->_slots[$key][0], $this->_slots[$key][1], $this->_slots[$key][2]);
            }
        } else if ($this->_parentContext) {
            return $this->_parentContext->echoSlot($key);
        }
    }