title: How to determine if a given request is running?
body: <p>I'm looking at retrofit for my networking layer. Is there any way to tell if a particular async request is running at any given moment?</p>
  
  <p>For example, I'd like to know if a request is running so that I can update the user interface at various times. I could do this myself by keeping variables around to track state, but wondering if there's something already in the library for this.</p>