* The returned collection is unmodifiable.
     *
     * @see #addSourceRoot(SourceRoot)
     */
    public Collection<SourceRoot> getSourceRoots() {
        return Collections.unmodifiableCollection(sources);
    }

    /**
     * {@return all enabled sources that provide files in the given language for the given scope}.

  private static class GenericClass<T> {
    private interface Base {}
  }

  private static IterableSubject makeUnmodifiable(Collection<?> actual) {
    return assertThat(Collections.<Object>unmodifiableCollection(actual));
  }