dEdge</a> returns null, this method creates a new <a href="LayoutEdge.html" class="tsd-kind-class">LayoutEdge</a>,
makes sure the <a href="Link.html#fromNode" class="tsd-kind-accessor">Link.fromNode</a> and <a href="Link.html#toNode" class="tsd-kind-accessor">Link.toNode</a> have
corresponding <a href="LayoutVertex.html" class="tsd-kind-class">LayoutVertex</a>es in the network, and adds the edge itself
to the network.</p>
</div><div class="tsd-parameters"><h4 class="tsd-parameters-title">Parameters</h4><ul 