code: public boolean containsChild(final AbstractHtml childTag) {
  
          final Lock lock = sharedObject.getLock(ACCESS_OBJECT).readLock();
          try {
              lock.lock();
  
              return children.contains(childTag);
          } finally {
              lock.unlock();
          }
      }
docs: Checks whether a tag is contained in its direct children. An efficient
  way to check if the given tag is a direct child of this tag.
  
  @param childTag
  @return true if the given tag is a child of this tags.
  @since 3.0.1
  @author WFF