*
     * @param severity the severity level to get problems for
     * @return a stream of problems with the specified severity
     */
    @Nonnull
    Stream<P> problems(BuilderProblem.Severity severity);

    /**
     * Creates an "empty" problem collector that doesn't store any problems.
     *
     * @param <P> the type of problem
     * @return an empty problem collector
     */
    @Nonnull

    }

    public void add(ModelProblem problem) {
        problems.add(problem);

        severities.add(problem.getSeverity());
    }

    public void addAll(List<ModelProblem> problems) {
        this.problems.addAll(problems);

        for (ModelProblem problem : problems) {
            severities.add(problem.getSeverity());
        }
    }

    @Override

    }

    @Override
    public List<Problem> getProblems() {
        return problems;
    }

    @Override
    public void setSource(String source) {
        this.source = source;
    }

    @Override
    public void add(Problem.Severity severity, String message, int line, int column, Exception cause) {
        Problem problem = new DefaultProblem(message, severity, source, line, column, cause);

        collector.add(Problem.Severity.ERROR, "Error message", 10, 5, null);
        collector.add(Problem.Severity.WARNING, "Warning message", 15, 3, null);

        List<Problem> problems = collector.getProblems();
        assertEquals(2, problems.size(), "Should collect both problems");
        assertEquals(Problem.Severity.ERROR, problems.get(0).getSeverity(), "First problem should be ERROR");

            file.forEachLine(Charsets.UTF_8) {
                val (version, _, problem, relativePath, lineNumber) = it.split(';')
                byCategory.getOrPut(toCategory(version, file.nameWithoutExtension)) {
                    mutableMapOf()
                }.getOrPut(file.nameWithoutExtension) {
                    mutableSetOf()
                }.add(Problem(name = problem, relativePath = relativePath, lineNumber = lineNumber.toInt()))
            }

     * @param line The one-based index of the line containing the problem or {@code -1} if unknown.
     * @param column The one-based index of the column containing the problem or {@code -1} if unknown.
     * @param cause The cause of the problem, may be {@code null}.
     */
    void add(Problem.Severity severity, String message, int line, int column, Exception cause);

    /**

    private List<Problem> problems;

    /**
     * Default constructor
     *
     * @param effectiveToolchains the merged toolchains, may not be {@code null}
     * @param problems the problems while building the effectiveToolchains, if any.
     */
    public DefaultToolchainsBuildingResult(PersistedToolchains effectiveToolchains, List<Problem> problems) {
        this.effectiveToolchains = effectiveToolchains;

     * @param problems the collection of problems to include in the message
     * @return a formatted message including details of all problems
     */
    protected static String buildMessage(String message, ProblemCollector<BuilderProblem> problems) {
        StringBuilder msg = new StringBuilder(message);
        problems.problems().forEach(problem -> msg.append("\n * ")
                .append(problem.getSeverity().name())

        return null;
    }

    static String toMessage(String modelId, List<ModelProblem> problems) {
        StringWriter buffer = new StringWriter(1024);

        PrintWriter writer = new PrintWriter(buffer);

        writer.print(problems.size());
        writer.print((problems.size() == 1) ? " problem was " : " problems were ");
        writer.print("encountered while building the effective model");

        return Stream.of(problems).map(String::trim).filter(s -> s.isEmpty() == false).collect(Collectors.joining("\n"));
    }

    private String checkNoneExists(String message, Stream<? extends Class<?>> stream) {
        String problem = stream.map(each -> "  * " + each.getName()).sorted().collect(Collectors.joining("\n"));
        if (problem.isEmpty() == false) {
            return message + ":\n" + problem;