>
  returns the first selected <a>Part</a>, which might be either a <a>Node</a>, a <a>Link</a>,
  or null if nothing is selected.
</p>
<p>
  If you remember the selected Node or Link, you can then examine it further more easily. For example:
</p>
<pre class="lang-js"><code>
myNode = myDiagram.selection.first(); // get a reference to the first selected Part
myNode.data.key // inspect its data.key
myNode.data // or look at the whole data object
</code></pre>
<p>
  You could also look at other properties of th