code: private void addInWffIdMap(final AbstractHtml tag) {
  
          final Deque<Set<AbstractHtml>> childrenStack = new ArrayDeque<>();
          // passed 2 instead of 1 because the load factor is 0.75f
          final Set<AbstractHtml> initialSet = new HashSet<>(2);
          initialSet.add(tag);
          childrenStack.push(initialSet);
  
          Set<AbstractHtml> children;
          while ((children = childrenStack.poll()) != null) {
              for (final AbstractHtml child : children) {
  
                  final DataWffId wffIdAttr = child.getDataWffId();
  
                  if (wffIdAttr != null) {
                      tagByWffId.put(wffIdAttr.getValue(), child);
                  }
  
                  final Set<AbstractHtml> subChildren = child
                          .getChildren(accessObject);
                  if (subChildren != null && subChildren.size() > 0) {
                      childrenStack.push(subChildren);
                  }
  
              }
          }
  
      }
docs: adds to wffid map
  
  @param tag
  @since 2.0.0
  @author WFF