docs: function () {
              var cfg = this._cfg;
  
              // invalid text and value shouldn't be set at the same time
              var text = cfg.invalidText || "";
  
              if (text && cfg.value) {
                  // There's both a value and an invalid text, prefer the value
                  this.setProperty("invalidText", null);
                  text = "";
              }
  
              // Validate the value in the configuration
              var res = this.checkValue({
                  text : text,
                  value : cfg.value,
                  performCheckOnly : true
              });
  
              if (res.report) {
                  var report = res.report;
                  if (!text && report.text != null) {
                      text = '' + report.text; // String cast of valid value
                  }
                  report.$dispose();
              }
              if (!text) {
                  text = this._getPrefilledText(cfg.prefill);
              }
  
              return text;
          }