docs: protected void createEventVertex(FlowElement flowElement) {
      // Add styling for events if needed
      if (!graph.getStylesheet().getStyles().containsKey(STYLE_EVENT)) {
        Hashtable<String, Object> eventStyle = new Hashtable<String, Object>();
        eventStyle.put(mxConstants.STYLE_SHAPE, mxConstants.SHAPE_ELLIPSE);
        graph.getStylesheet().putCellStyle(STYLE_EVENT, eventStyle);
      }
  
      // Add vertex representing event to graph
      Object eventVertex = graph.insertVertex(cellParent, flowElement.getId(), "", 0, 0, eventSize, eventSize, STYLE_EVENT);
      generatedVertices.put(flowElement.getId(), eventVertex);
    }