code: private Stream<AbstractHtml> buildNestedChildrenIncludingParent() {
          return Stream.concat(Stream.of(this), children.stream()
                  .flatMap(AbstractHtml::buildNestedChildrenIncludingParent));
      }
docs: NB: it might lead to StackOverflowException if the tag hierarchy is deep.
  
  @return stream of all nested children including this parent object.
  @since 3.0.0
  @author WFF