如何在plotly (python) sankey中显示一个图例？

import plotly.graph_objects as go
from plotly.subplots import make_subplots

fig = go.Figure(data=[go.Sankey(
    # sankey图的节点
    node=dict(
        # 节点的标签和颜色
        label=["A", "B", "C", "D", "E"],
        color=["blue", "green", "red", "purple", "orange"]
    ),
    # sankey图的连接
    link=dict(
        # 连接的源节点、目标节点和值
        source=[0, 1, 2, 3, 3],
        target=[2, 3, 4, 4, 2],
        value=[8, 4, 2, 2, 4]
    )
)])

# 创建一个子图布局
fig_subplots = make_subplots(rows=1, cols=2)

# 在第一个子图中添加sankey图
fig_subplots.add_trace(fig.data[0])

# 在第二个子图中添加自定义注释
fig_subplots.add_trace(go.Scatter(
    x=[None], y=[None], mode='markers',
    marker=dict(size=0, color='rgba(0,0,0,0)'),
    legendgroup='legend', showlegend=True,
    name='Legend', hoverinfo='none'
))

# 更新布局
fig_subplots.update_layout(showlegend=True)

# 显示图形
fig_subplots.show()