code: function() {
  
              var form = this.element.getElementsByTagName("form")[0];
  
              if (this.form) {
                  if (this.form == form && Dom.isAncestor(this.element, this.form)) {
                      return;
                  } else {
                      Event.purgeElement(this.form);
                      this.form = null;
                  }
              }
  
              if (!form) {
                  form = document.createElement("form");
                  form.name = "frm_" + this.id;
                  this.body.appendChild(form);
              }
  
              if (form) {
                  this.form = form;
                  Event.on(form, "submit", this._submitHandler, this, true);
              }
          }
docs: Prepares the Dialog's internal FORM object, creating one if one is
  not currently present.
  @method registerForm