code: static Optional<Entity> getOpt(CheckedDatastoreReaderWriter datastore, Key key) throws IOException {
      return Optional.ofNullable(datastore.get(key));
    }
docs: Optionally get an {@link Entity} from a {@link DatastoreReader}.
  
  @param datastore  The reader to get from
  @param key              The key to get
  @return an optional containing the entity if it existed, empty otherwise.