code: List<Entity> get(Iterable<Key> keys) throws IOException {
      return call(() -> ImmutableList.copyOf(rw.get(toArray(keys, Key.class))));
    }
docs: Only use this method if the results are small enough that gathering them in list is acceptable.
  Otherwise use {@link #get(Iterable, IOConsumer)}.
  @see DatastoreReaderWriter#get(Key...)
  @throws IOException if the underlying client throws {@link DatastoreException}