@Override
    public int write(OutputStream out, boolean withTags) throws IOException {
      // This type of Cell is used only to maintain some internal states. We never allow this type
      // of Cell to be returned back over the RPC
      throw new IllegalStateException("A reader should never return this type of a Cell");
    }
A setter that helps to avoid object creation every time and whenever there is a need to
create new KeyOnlyKeyValue.
@param key    Key to set
@param offset Offset of the Key
@param length length of the Key
hbase-common/src/main/java/org/apache/hadoop/hbase/KeyValue.java