() => {
  class MyForm extends Component {
    constructor(props) {
      super(props);

      this.state = {
        indeterminate: true
      };

      this.handleChange = this.handleChange.bind(this);
    }

    handleChange(event) {
      this.setState((prevState) => ({
        indeterminate: !prevState.indeterminate
      }));
    }

    render() {
      return (
        <DemoForm>
          <Checkbox
            name="indeterminate"
            label="Indeterminate"
            value="indeterminate"
            indeterminate={this.state.indeterminate}
            onChange={this.handleChange} />
        </DemoForm>
      );
    }
  }

  return <MyForm />;
}