sion of <a href="validation.html">Linking Validation</a>.
</p>
<p>
  By setting <a>GraphObject.toMaxLinks</a> to 1, as shown in this example, the user may draw at most one link going into that port.
  And because <a>GraphObject.fromLinkable</a> is false for that port element, the user will not be able to connect any links coming out of that port.
</p>
<p>
  If you want to prevent the user from connecting any more than one Link with a Node, regardless of direction,
  you will need to implement a <a>LinkingBa