title: How to get the source of a property by subscribing to an event stream?
body: <p>if I have a JavaFX property and I create an event stream from this property:</p>
  
  <pre><code>EventStreams.nonNullValuesOf(node.boundsInParentProperty())
  </code></pre>
  
  <p>Is there a possibility to set the source (in this case the "node") at creation time or to get this object later in a subscription?</p>
  
  <p>For example:</p>
  
  <pre><code>EventStream&lt;...&gt; stream = EventStreams.nonNullValuesOf(node.boundsInParentProperty());
  
  ...
  stream.subscribe((node, bounds) -&gt; ...);
  </code></pre>
  
  <p>or at creation time:</p>
  
  <pre><code>EventStream&lt;...&gt; stream = EventStreams.valueAndSource(node.boundsInParentProperty(), node);
  </code></pre>