title: Flip map key-value pair
body: <p>I have a map. I want to flip the key-value so that it not becomes map. So basically the value of the first map becomes the key of the second map. How do i do this?</p>
  
  <p>Example map:</p>
  
  <pre><code>1 - 1.0
  2 - 2.0
  </code></pre>
  
  <p>After flip</p>
  
  <pre><code>1.0 - 1
  2.0 - 2
  </code></pre>