old_contents: import React, {Component} from 'react';
  
  export default class NotFound extends Component {
    render() {
      return (
        <div className="container">
          <h1>Doh! 404!</h1>
          <p>These are <em>not</em> the droids you are looking for!</p>
        </div>
      );
    }
  }
  
new_contents: import React from 'react';
  
  export default function NotFound() {
    return (
        <div className="container">
        <h1>Doh! 404!</h1>
        <p>These are <em>not</em> the droids you are looking for!</p>
        </div>
    );
  }
  
subject: Make stateless components simple functions