@Override
  public void writeTo(OutputStream out) throws IOException {
    // No usage of this API in code. Just making it as an Unsupported operation as of now
    throw new UnsupportedOperationException();
  }
An OutputStream which writes data into ByteBuffers. It will try to get ByteBuffer, as and when
needed, from the passed pool. When pool is not giving a ByteBuffer it will create one on heap.
Make sure to call {@link #releaseResources()} method once the Stream usage is over and data is
transferred to the wanted destination. Not thread safe!
hbase-common/src/main/java/org/apache/hadoop/hbase/io/ByteBufferListOutputStream.java