code: func (f *FileStore) Retrieve(ctx context.Context, addr Address) (reader *LazyChunkReader, isEncrypted bool) {
  	isEncrypted = len(addr) > f.hashFunc().Size()
  	getter := NewHasherStore(f.ChunkStore, f.hashFunc, isEncrypted)
  	reader = TreeJoin(ctx, addr, getter, 0)
  	return
  }
docs: // Retrieve is a public API. Main entry point for document retrieval directly. Used by the
  // FS-aware API and httpaccess
  // Chunk retrieval blocks on netStore requests with a timeout so reader will
  // report error if retrieval of chunks within requested range time out.
  // It returns a reader with the chunk data and whether the content was encrypted