title: How to add two different fields using timelion
body: <p>.es(metric='sum:completed','sum:cancelled')</p>
  
  <p>I have value in 2 different fields <code>completed</code> and <code>cancelled</code>, now I am trying to add values in above . What is the right way ? </p>
  
  <p>I tried above but it fails .</p>