title: How check if value exists in request POST?
body: <p>I submit form using POST method. Form has one input field: <code>time</code>.</p>
  
  <p>I tried to check if exist parameter: </p>
  
  <pre><code>if 'time' in request.data:
     pass
  </code></pre>
  
  <p>But it does not work</p>