ns for the cluster node. All options
                    described
                    in the <a href="./nodes.html">nodes module</a> are allowed. This allows you to style your cluster
                    node
                    any way you want. This is also the style object that is provided in the processProperties function
                    for
                    fine tuning. If undefined, default node options will be used.<br/><br/>
                    Default functionality only allows clustering if