code: @Override
      public final Iterable<TrailerDocument> findAll(
              final RootDocument rootDocument) {
          final Iterable<TrailerDocument> trailerDocuments =
                  findAll(rootDocument.getFilename());
          if (trailerDocuments == null) {
              return null;
          }
          for (final TrailerDocument trailerDocument : trailerDocuments) {
              final Trailer trailer = trailerDocument.getGedObject();
              trailer.setParent(rootDocument.getGedObject());
          }
          return trailerDocuments;
      }
docs: {@inheritDoc}