that are
                    selected to be in the cluster and calls this function with their data as argument.
                    If this function returns true, this node will be added to the cluster. You have access to all
                    options
                    (including the default)
                    as well as any custom fields you may have added to the node to determine whether or not to include
                    it in
                    the cluster. Example:
<pre class="prettyprint lan