code: @Override
      public final Iterable<HeadDocument> findAll(final String filename) {
          final Query searchQuery =
                  new Query(Criteria.where("filename").is(filename));
          final List<HeadDocumentMongo> headDocumentsMongo =
                  mongoTemplate.find(searchQuery, HeadDocumentMongo.class);
          if (headDocumentsMongo == null) {
              return null;
          }
          final List<HeadDocument> headDocuments = new ArrayList<>();
          for (final HeadDocument headDocument : headDocumentsMongo) {
              final Head head =
                      (Head) toObjConverter.createGedObject(null, headDocument);
              headDocument.setGedObject(head);
              headDocuments.add(headDocument);
          }
          return headDocuments;
      }
docs: {@inheritDoc}