 number of shape figures, one of which the user can click to replace the node's
    shape's figure. These tab panels use a "Flow" PanelLayout to arrange the shapes in rows, by setting <a>PanelLayoutFlow.direction</a> to 0. Note how for
    a custom <a>PanelLayout</a> one cannot use its name directly, but must construct and initialize an instance of the PanelLayout.
  </p>
  <p>This extension is defined in its own file, as <a href="../extensions/PanelLayoutFlow.js">PanelLayoutFlow.js</a>.</p>
</div>

       