code: public ContainerTag with(Iterable<? extends DomContent> children) {
          if (children != null) {
              for (DomContent child : children) {
                  this.with(child);
              }
          }
          return this;
      }
docs: Appends a list of DomContent-objects to the end of this element
  
  @param children DomContent-objects to be appended
  @return itself for easy chaining