public function toOptionArray() {
        return [
            [
                'value' => self::MODE_CARDS,
                'label' => __('Cards')
            ],
            [
                'value' => self::MODE_MIXED,
                'label' => __('Mixed')
            ],
            [
                'value' => self::MODE_LOCAL,
                'label' => __('Local payments')
            ] 
        ];
    }