public void appendData(final Key key, final T data) throws IOException {
    synchronized (myDataLock) {
      myMap.appendData(key, new AppendablePersistentMap.ValueDataAppender() {
        @Override
        public void append(@NotNull DataOutput out) throws IOException {
          myStateExternalizer.save(out, data);
        }
      });
    }
  }
public void appendData(final Key key, final T data)