如何在plotly（python）sankey中显示图例？

我想为一份报告绘制一些代表不同物质质量流的sankey图表。我想用图例来区分这些物质，但我不知道怎么做。我尝试了

showlegend

，但没有成功

import plotly.graph_objects as go

fig = go.Figure(data=[go.Sankey(
    node = dict(
      pad = 15,
      thickness = 20,
      line = dict(color = "black", width = 0.5),
      label = ['household','industry','waste'],
      color = "blue"
    ),
    link = dict(
      source = [0,1,0,1], # indices correspond to labels, eg A1, A2, A2, B1, ...
      target = [2,2,2,2],
      value = [7190,2074,4483,74.50],
      label = ['aluminium','aluminium','copper','copper'],
      color = ['#d7d6d6','#d7d6d6','#f3cf07','#f3cf07']
  ))])
fig.update_layout(showlegend=True)
fig.show() 

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尽管文档目前似乎表明它们确实支持图例，但Plotly Sankey traces似乎并不支持图例

我已经在Plotly repo上创建了；看起来，该决议可能会改进文档以使其更清晰