this.solutions = new ArrayList<String>();
        }
        this.solutions.add(solution);
        return this;
    }

    @Override
    @SuppressWarnings("unchecked")
    public <U extends AdditionalDataSpec> InternalProblemBuilder additionalData(Class<? extends U> specType, Action<? super U> config) {
        if (!supportedAdditionalDataTypes.contains(specType)) {