docs: private List<File> getSchemaFilesFrom(Set<File> files) {
      return FluentIterable.from(files).filter(new Predicate<File>() {
        @Override public boolean apply(@Nullable File file) {
          return file != null && file.getName().equals(GraphQLSourceDirectorySet.SCHEMA_FILE_NAME);
        }
      }).toSortedList(new Comparator<File>() {
        @Override public int compare(File o1, File o2) {
          String sourceSet1 = getSourceSetNameFromFile(o1);
          String sourceSet2 = getSourceSetNameFromFile(o2);
          // negative because the sourceSets list is in reverse order
          return -(sourceSets.indexOf(sourceSet1) - sourceSets.indexOf(sourceSet2));
        }
      });
    }