class UpgradeJavaMessage {

    /**
     * The reason why the language level must be upgraded.
     */
    private final String reason;

    /**
     * The language level that must be configured.
     */
    private final ParserConfiguration.LanguageLevel level;

    /**
     * Contructor.
     * @param reason The reason why the language level must be upgraded.
     * @param level The language level that must be configured.
     */
    UpgradeJavaMessage(
        final String reason,
        final ParserConfiguration.LanguageLevel level
    ) {
        this.reason = reason;
        this.level = level;
    }

    @Override
    public String toString() {<FILL_FUNCTION_BODY>}
}

        return String.format(
            "%s Pay attention that this feature is supported starting from '%s' language level. If you need that feature the language level must be configured in the configuration before parsing the source files.",
            this.reason,
            this.level.toString()
        );
    
<no_super_class>