code: function(fieldName, text, onValid) {
        var isValid = this.model.isValid(fieldName);
        if ((onValid ? true : false) === (isValid ? true : false)) {
          return {
            text: text
          };
        } else {
          return {
            text: ''
          };
        }
      }
docs: For use in a feedback's "then" callback
  Checks to see if the form model's field is valid. If the field is invalid, it sets the text.
  If the field is invalid, it removes the text. When an array is passed in for the fieldName,
  it will validate all the fields together as if they were one (any failure counts as a total failure,
  and all fields need to be valid for success).
  @param fieldName {String or Array<String>} the name of the form model field or an array of field names
  @param text {String} the text to set
  @param [onValid] {Boolean} if true, will reverse the logic operator
  @private
  @method _thenAddTextIfInvalid