public function addLabel(Doozr_Form_Service_Component_Interface_Html $label)
    {
        $index               = $this->addChild($label);
        $this->index[$index] = self::LABEL;

        (!isset($this->indexReverse[self::LABEL])) ? $this->indexReverse[self::LABEL] = [] : null;
        $this->indexReverse[self::LABEL][]                                            = $index;

        return $index;
    }