code: public LocalFsBlobStoreFile read(String key) throws IOException {
          return new LocalFsBlobStoreFile(getKeyDir(key), BlobStoreFile.BLOBSTORE_DATA_FILE);
      }
docs: Get an input stream for reading a part.
  @param key the key of the part to read.
  @return the where to read the data from.
  @throws IOException on any error