content: import React from 'react';
  import { Link } from 'react-router-dom';
  
  export class Header extends React.Component {
      render() {
          return (
              <nav className="navbar navbar-default">
                  <div className="container">
                      <div className="navbar-header">
                          <ul className="nav navbar-nav">
                              <ul>
                                  <li><Link to="/">Home</Link></li>
                                  <li><Link to="/login">About</Link></li>
                              </ul>
                          </ul>
                      </div>
                  </div>
              </nav>
          );
      }
  }