title: Rx js understanding the lift method
body: <p>I want to create a new operator and I find in the <a href="https://github.com/ReactiveX/rxjs/blob/master/doc/operator-creation.md" rel="noreferrer">documentation</a> that one of the ways is to do something like this:</p>
  
  <pre><code>class MyObservable extends Observable {
    lift(operator) {
      const observable = new MyObservable()
      observable.source = this;
      observable.operator = operator;
      return observable;
    }
  
    // put it here .. or ..
    customOperator() {
      /* do things and return an Observable */
    }
  }
  
  // ... put it here...
  MyObservable.prototype.mySimpleOperator = mySimpleOperator;
  </code></pre>
  
  <p>I don't understand what is the <code>lift</code> method and what is going on here, can someone help, please? </p>