title: Groovy not in collection
body: <p>The groovy way to see if something is in a list is to use "in"</p>
  
  <pre><code>   if('b' in ['a','b','c'])
  </code></pre>
  
  <p>However how do you nicely see if something is not in a collection?</p>
  
  <pre><code>  if(!('g' in ['a','b','c']))
  </code></pre>
  
  <p>Seems messy and the "!" is hidden to the casual glance.   Is there a more idiomatic groovy way to do this?</p>
  
  <p>Thanks!</p>