title: RxJava2 Difference between as(), to() and compose()
body: <p>These words are difficult to search online, so I can't find any information on them besides the docs, which seems to me to have almost the same description (specially for <code>as</code> and <code>to</code>).</p>
  
  <p>What's the difference between <code>as()</code>, <code>to()</code> and <code>compose()</code> in RxJava2? When should I use any of them?</p>