code: public Example addChild()
      {
          if (hasChild())
          {
              return child.addSibling();
          }
          else
          {
              if (childTags.isEmpty()) throw new IllegalStateException( "No child tag" );
              List<String> moreTags = new ArrayList<String>( childTags );
              String childTag = firstPattern( CollectionUtil.shift( moreTags ) );
              child = createSpecification( childTag, moreTags );
              return child;
          }
      }
docs: <p>addChild.</p>
  
  @return a {@link com.greenpepper.Example} object.