code: @Override
      public final TrailerDocument findByRootAndString(
              final RootDocument rootDocument, final String string) {
          final TrailerDocument trailerDocument =
                  findByFileAndString(rootDocument.getFilename(), string);
          if (trailerDocument == null) {
              return null;
          }
          final Trailer trailer = trailerDocument.getGedObject();
          trailer.setParent(rootDocument.getGedObject());
          return trailerDocument;
      }
docs: {@inheritDoc}