public static List<Tag> carryForwardTags(final List<Tag> tagsOrNull, final ExtendedCell cell) {
    Iterator<Tag> itr = PrivateCellUtil.tagsIterator(cell);
    if (itr == EMPTY_TAGS_ITR) {
      // If no Tags, return early.
      return tagsOrNull;
    }
    List<Tag> tags = tagsOrNull;
    if (tags == null) {
      tags = new ArrayList<>();
    }
    while (itr.hasNext()) {
      tags.add(itr.next());
    }
    return tags;
  }
Add to <code>tagsOrNull</code> any Tags <code>cell</code> is carrying or null if none.
hbase-common/src/main/java/org/apache/hadoop/hbase/TagUtil.java