code: private boolean isStreamPresentAndWritable(int streamId) {
          final Http2Stream stream = encoder.connection().stream(streamId);
          if (stream == null) {
              return false;
          }
  
          switch (stream.state()) {
              case RESERVED_LOCAL:
              case OPEN:
              case HALF_CLOSED_REMOTE:
                  return true;
              default:
                  // The response has been sent already.
                  return false;
          }
      }
docs: Returns {@code true} if the stream with the given {@code streamId} has been created and is writable.
  Note that this method will return {@code false} for the stream which was not created yet.