title: Value of type 'Observable<String>' has no member 'bind'
body: <p>I am trying to bind a string value in ViewModel to a label in my ViewController but I am getting following error:</p>
  
  <blockquote>
    <p>Value of type 'Observable' has no member 'bind'
    My code for binding in ViewController:</p>
  </blockquote>
  
  <pre><code>self.viewModel.myNum
          .map( { $0 })
          .bind(to: serialNumberLabel.rx.text)
  </code></pre>
  
  <p>myNum is defined in viewModel as following:</p>
  
  <pre><code>var myNum: Observable&lt;String&gt;
  </code></pre>
  
  <p>No I have 2 problems here:
  1. Above error in ViewController
  2. Initializing myNum in ViewModel
  I tried following for initializing myNum but I am getting error:</p>
  
  <pre><code>materialNum = Observable&lt;String&gt;("")
  </code></pre>