docs: public void reader() throws IOException {
      // [START reader]
      try (ReadChannel reader = blob.reader()) {
        ByteBuffer bytes = ByteBuffer.allocate(64 * 1024);
        while (reader.read(bytes) > 0) {
          bytes.flip();
          // do something with bytes
          bytes.clear();
        }
      }
      // [END reader]
    }