var target = e.detail.target;
      if (target) {
        var index = this._customElements.indexOf(target);
        if (index > -1) {
          this._customElements.splice(index, 1);
          this._customElementsInitialValues.splice(index, 1);
        }
      }
    },

    /**
     * Validates all the required elements (custom and native) in the form.
     * @return {boolean} True if all the elements are valid.
     */
    validate: function() {
      var valid = true;

      // Validate all the custom ele