class Problem {

    private final String message;

    private final TokenRange location;

    private final Throwable cause;

    public Problem(String message, TokenRange location, Throwable cause) {
        assertNotNull(message);
        this.message = message;
        this.location = location;
        this.cause = cause;
    }

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

    /**
     * @return the message that was passed into the constructor.
     */
    public String getMessage() {
        return message;
    }

    /**
     * @return the message plus location information.
     */
    public String getVerboseMessage() {
        return getLocation().map(l -> l.getBegin().getRange().map(r -> r.begin.toString()).orElse("(line ?,col ?)") + " " + message).orElse(message);
    }

    /**
     * @return the location that was passed into the constructor.
     */
    public Optional<TokenRange> getLocation() {
        return Optional.ofNullable(location);
    }

    /**
     * @return the cause that was passed into the constructor.
     */
    public Optional<Throwable> getCause() {
        return Optional.ofNullable(cause);
    }

    /**
     * Sorts problems on position.
     */
    public static Comparator<Problem> PROBLEM_BY_BEGIN_POSITION = (a, b) -> {
        final Optional<Position> aBegin = a.getLocation().flatMap(l -> l.getBegin().getRange().map(r -> r.begin));
        final Optional<Position> bBegin = b.getLocation().flatMap(l -> l.getBegin().getRange().map(r -> r.begin));
        if (aBegin.isPresent() && bBegin.isPresent()) {
            return aBegin.get().compareTo(bBegin.get());
        }
        if (a.getLocation().isPresent() || b.getLocation().isPresent()) {
            if (a.getLocation().isPresent()) {
                return 1;
            }
            return -1;
        }
        return 0;
    };
}

        final StringBuilder str = new StringBuilder(getVerboseMessage());
        if (cause != null) {
            str.append(SYSTEM_EOL).append("Problem stacktrace : ").append(SYSTEM_EOL);
            for (int i = 0; i < cause.getStackTrace().length; i++) {
                StackTraceElement ste = cause.getStackTrace()[i];
                str.append("  ").append(ste.toString());
                if (i + 1 != cause.getStackTrace().length)
                    str.append(SYSTEM_EOL);
            }
        }
        return str.toString();
    
<no_super_class>