code: void updateClusterXY(int cluster, Point2D pt) {
  		int vertexList = getClusterVertices(cluster);
  		for (int vh = m_cluster_vertices.getFirst(vertexList); vh != -1; vh = m_cluster_vertices
  				.getNext(vh)) {
  			int vertex = m_cluster_vertices.getElement(vh);
  			m_shape.setXY(vertex, pt);
  		}
  	}
docs: Updates all vertices of the cluster to new coordinate