code: func (f *Field) mergeRemoteAvailableShards(b *roaring.Bitmap) {
  	f.mu.Lock()
  	defer f.mu.Unlock()
  	f.remoteAvailableShards = f.remoteAvailableShards.Union(b)
  }
docs: // mergeRemoteAvailableShards merges the set of available shards into the current known set.