Sankey

trace = go.Sankey(
    node=dict(
        label=["A1", "A2"]+["B1", "B2"]+["C1", "C2"],
        #        0     1      2     3      4     5
        # thickness=20,
        # line=dict(color="black", width=0.5),
        # pad=15,
        color=["blue"]*2 + ['red']*2 + ['green']*2
    ),
    link=dict(
        source=[0, 1, 1, 0, 2, 3, 3],
        target=[2, 2, 3, 3, 4, 4, 5],
        value= [8, 3, 4, 2, 8, 4, 2]
    )
)
layout = go.Layout(title="Sankey diagram")
fig = go.Figure(trace, layout)
fig.show()