No draw when represent node with int type

[eggplantisme]

When I try to draw a hypergraph with int type, use draw() to visualize it, it will render no hypergraph:

hg = HypergraphDB()

# 添加社交网络数据
hg.add_v(1, {"name": "Alice", "age": 30, "city": "北京"})
hg.add_v(2, {"name": "Bob", "age": 24, "city": "上海"})
hg.add_v(3, {"name": "Charlie", "age": 28, "city": "深圳"})
hg.add_v(4, {"name": "David", "age": 35, "city": "广州"})


# 二元关系
hg.add_e((1, 2), {"relation": "朋友", "since": "2020"})
hg.add_e((2, 3), {"relation": "同事", "company": "科技公司"})

# 群体关系（超图的威力所在！）
hg.add_e((1, 2, 3), {"relation": "学习小组", "subject": "机器学习"})
hg.add_e((1, 3, 4), {"relation": "项目团队", "project": "网页应用"})

# # 启动可视化
# hg.draw()

So for now, is the draw only support str type of nodes?