title: How to optimize CSS background-image and background-position properties
body: <p>I'm following a tutorial on front-end development, and I just wrote this ruleset for a header image:</p>
  
  <pre class="lang-css prettyprint-override"><code>header {
      background-image: linear-gradient(#00000070, #00000070), url("../img/hero.jpg");
      background-position: center;
      background-size: cover;
      height: 100vh;
  }
  </code></pre>
  
  <p>PyCharm tells me the <code>background-image</code> and <code>background-position</code> properties can be optimized by transforming them to a shorthand form, but it doesn't provide specific advice on how. As I'm a beginner to CSS, I can't infer the problem, and w3schools.com didn't offer any shorthand. How else can I write this block to shorten it?</p>