title: Immutable.js prints a warning on accessing .length of a List
body: <p>I've searched everywhere but don't seem to find the solution.</p>
  
  <p>When mapping my data, I want to get the length of a List I have in my state:</p>
  
  <pre><code>state.substate.get('myList').length
  </code></pre>
  
  <p>But it throws a warning telling me to use the <code>size</code> property or <code>count()</code> function and can't figure out how to use it on a state property I am getting.</p>
  
  <p>How should I be doing it?
  Thanks :)</p>