public onExecute(event: IListViewCommandSetExecuteEventParameters): void {
        switch (event.itemId) {
          case 'COMMAND_1':
            Dialog.alert(`${this.properties.sampleTextOne}`);
            break;
          case 'COMMAND_2':         
          const div = document.createElement('div');
        const element: React.ReactElement<{} > = React.createElement(
          MyCustomPanel,
          {
            
          }
        );
        ReactDom.render(element, div);    
          break;    
          default:
            throw new Error('Unknown command');
        }
      }