@Override
    public int getTagsLength() {
      if (null == this.tags) {
        // Nulled out tags array optimization in constructor
        return 0;
      }
      return this.tags.length;
    }
Construct a TagRewriteCell
@param cell The original Cell which it rewrites
@param tags the tags bytes. The array suppose to contain the tags bytes alone.
hbase-common/src/main/java/org/apache/hadoop/hbase/PrivateCellUtil.java