public static function getClasses() : array
    {
        return [
            self::CLASS_0 => self::CLASS_0,
            self::CLASS_1 => self::CLASS_1,
            self::CLASS_2 => self::CLASS_2,
            self::CLASS_3 => self::CLASS_3
        ];
    }
public static function getClasses() : array
    {
        return [
            self::CLASS_0 => self::CLASS_0,
            self::CLASS_1 => self::CLASS_1,
            self::CLASS_2 => self::CLASS_2,
            self::CLASS_3 => self::CLASS_3
        ];
    }
public static function getClasses ( ) : array { return [ self :: CLASS_0 => self :: CLASS_0 , self :: CLASS_1 => self :: CLASS_1 , self :: CLASS_2 => self :: CLASS_2 , self :: CLASS_3 => self :: CLASS_3 ] ; }
Returns the possible classes for the payload

@return array
Returns the possible classes for the payload