old_contents: import React, { Component } from 'react';
  import logo from './logo.svg';
  import './App.css';
  
  class App extends Component {
    render() {
      return (
        <div className="App">
          <div className="App-header">
            <img src={logo} className="App-logo" alt="logo" />
            <h2>Welcome to React</h2>
          </div>
          <p className="App-intro">
            To get started, edit <code>src/App.js</code> and save to reload.
          </p>
        </div>
      );
    }
  }
  
  export default App;
  
new_contents: import React, { Component } from 'react';
  import logo from './logo.svg';
  import './App.css';
  
  class App extends Component {
      render() {
          return (
              <div className="App">
                  <div className="App-header">
                      <img src={logo} className="App-logo" alt="logo" />
                      <h2>Welcome to React</h2>
                  </div>
                  <p className="App-intro">
                      To get started, edit <code>src/App.js</code> and save to reload.
                  </p>
              </div>
          );
      }
  }
  
  export default App;
  
subject: sort code in App.js