Common/Model/NotificationTypes.php
static public function getTypes()
    {
        return [
            static::MANUAL,
            static::CART_REMIND,
            static::ORDER_ACCEPTED,
            static::QUOTE_REMIND,
            static::PAYMENT_CAPTURED,
            static::PAYMENT_EXPIRED,
            static::SHIPMENT_SHIPPED,
            static::SHIPMENT_PARTIAL,
            static::RETURN_PENDING,
            static::RETURN_RECEIVED,
        ];
    }
static public function getTypes()
    {
        return [
            static::MANUAL,
            static::CART_REMIND,
            static::ORDER_ACCEPTED,
            static::QUOTE_REMIND,
            static::PAYMENT_CAPTURED,
            static::PAYMENT_EXPIRED,
            static::SHIPMENT_SHIPPED,
            static::SHIPMENT_PARTIAL,
            static::RETURN_PENDING,
            static::RETURN_RECEIVED,
        ];
    }
Returns all the types.

@return array