title: Having trouble using React Transition Group first time
body: <p>Good day! I wrote this code to test the React transition group library and eventually get stuck with the error. The script gets run and I see the data fill form on the page styled but when I click submit button form does not disappear. Error reference description: Failed prop type: The prop <code>timeout</code> is marked as required in <code>CSSTransition</code>, but its value is <code>undefined</code>.
      in CSSTransition (at app.jsx:24)
      in App (at index.js:7) However transitionAppearTimeot={1500}!</p>
  
  <pre><code>import React, { Component } from 'react';
  import CSSTransitionGroup from 'react-transition-group/CSSTransition';
  import './app.css';
  import Form from './components/Form';
  class App extends Component {
  constructor() {
      super();
      this.state = {
          mounted: true,
      };
      this.handleSubmit = this.handleSubmit.bind(this);
  };
  handleSubmit(event) { 
      event.preventDefault();
      this.setState = {
          mounted: false
      }
      console.log(this.state);
  };
  
  render() {
      return (
          &lt;div className="app"&gt;
              &lt;CSSTransitionGroup
                  transitionName="fade"
                  transitionAppear={true}
                  transitionAppearTimeout={1500}
                  transitionEnter={false}
                  transitionLeave={true}
                  transitionLeaveTimeout={300}&gt;
                  {this.state.mounted &amp;&amp; &lt;Form onSubmit=
                  {this.handleSubmit} /&gt;}
              &lt;/CSSTransitionGroup&gt;
          &lt;/div&gt;
      );
    }
  }
  
  export default App;
  </code></pre>