docs: public Task updateDocument(Task task) throws ConflictException, DocumentStoreException {
          DocumentRevision rev = task.getDocumentRevision();
          rev.setBody(DocumentBodyFactory.create(task.asMap()));
          try {
              DocumentRevision updated = this.mDocumentStore.database().update(rev);
              return Task.fromRevision(updated);
          } catch (DocumentException de) {
              return null;
          }
      }