title: Finding the key in a map, given the value
body: <p>Hi I have a map like this :</p>
  
  <pre><code>[this:0, is:1, a:2, file:3, anotherkey:4, aa:5]
  </code></pre>
  
  <p>I wish I could find the <code>key</code>'s given the <code>value</code> of a map. For example, if the value <code>5</code> is given I need to return <code>aa</code> from the map.</p>
  
  <p>Is that possible?</p>