* @param problems The container used to collect problems that were encountered, must not be {@code null}.
     * @return The interpolated model, never {@code null}.
     */
    Model interpolateModel(Model model, File projectDir, ModelBuildingRequest request, ModelProblemCollector problems);

public class StringVisitorModelInterpolator extends AbstractStringBasedModelInterpolator {

    interface InnerInterpolator {
        String interpolate(String value);
    }

    @Override
    public Model interpolateModel(
            Model model, File projectDir, ModelBuildingRequest config, ModelProblemCollector problems) {
        List<? extends ValueSource> valueSources = createValueSources(model, projectDir, config, problems);