String prefix = getParameters().getPrefix().getOrElse("");

        return itemsToFilter()
            .filter(e -> e.getKey().startsWith(prefix))
            .collect(ImmutableMap.toImmutableMap(Map.Entry::getKey, Map.Entry::getValue));
    }

    protected abstract Stream<Map.Entry<String, String>> itemsToFilter();

    public interface Parameters extends MapWithPrefixedKeysValueSource.Parameters {
    }

    @Override
    protected Stream<Map.Entry<String, String>> itemsToFilter() {
        return System.getenv().entrySet().stream();
    }

    public interface Parameters extends MapWithPrefixedKeysValueSource.Parameters {
    }

    @Override
    protected Stream<Map.Entry<String, String>> itemsToFilter() {
        return System.getProperties().entrySet().stream()
            .filter(e -> e.getKey() instanceof String && e.getValue() instanceof String)
            .map(e -> {
                Map.Entry<?, ?> untypedEntry = e;

    }

    @Inject
    protected abstract GradleProperties getGradleProperties();

    @Override
    protected Stream<Map.Entry<String, String>> itemsToFilter() {
        return getGradleProperties().mergeProperties(new HashMap<>()).entrySet().stream()
            .filter(e -> e.getValue() instanceof String)
            .map(e -> {