docs: public DocumentRevisionTree getAllRevisionsOfDocument(final String docId) {
  
          try {
              return get(queue.submit(new GetAllRevisionsOfDocumentCallable(docId, this.attachmentsDir, this.attachmentStreamFactory)));
          } catch (ExecutionException e) {
              logger.log(Level.SEVERE, "Failed to get all revisions of document", e);
          }
          return null;
      }