ml" target="api">Tool</a>, or <a href="../api/symbols/Layout.html" target="api">Layout</a>.
  But when the desired property does not exist, you might need to override methods of CommandHandler, Tool, Layout, Link, or Node.
  Methods that you can override are documented in the API reference.
  Various features of GoJS can be overriden, either by replacing a method on an instance (a feature of JavaScript) or by defining a subclass.
  You should not modify the prototypes of any of the <b>GoJS</b> classes.
</p>