title: Opposite of switchMap operator in RxJava2
body: <p>I have configuration <code>Observable</code> to which I'm subscribing and launching my own <code>Observable</code> but I'm having a problem with canceling the running <code>Observable</code> upon receiving configuration update.</p>
  
  <p>I was thinking of something like <code>switchMap</code> operator but in reverse so when there's a new value from a source <code>Observable</code> we're unsubscribing from the mapped <code>Observable</code> and subscribing to a new one.</p>
  
  <p>Like this:</p>
  
  <pre><code>configuration.
      reverseSwitchMap {
          createMyObservable(it.somethingFromConfiguration) // this observable get's recreated for each configuration update
      }.subscribe {
          // here I'm receiving values from myObservable
      }
  </code></pre>
  
  <p>Is there an operator which could help me solve this problem?</p>