code: @Override
      public Collection<PersonDocument> findByRootAndSurname(
              final RootDocument rootDocument, final String surname) {
          if (rootDocument == null || surname == null) {
              return Collections.emptyList();
          }
          final Collection<PersonDocument> personDocuments = findByFileAndSurname(
                  rootDocument.getFilename(), surname);
          for (final PersonDocument personDocument : personDocuments) {
              final Person person = personDocument.getGedObject();
              person.setParent(rootDocument.getGedObject());
          }
          return personDocuments;
      }
docs: {@inheritDoc}