如何在plotly中为子图添加标签？

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

fig = make_subplots(rows=1, cols=2)

fig.add_trace(go.Scatter(x=[1, 2, 3], y=[4, 5, 6], name='子图1'), row=1, col=1)
fig.add_trace(go.Scatter(x=[1, 2, 3], y=[7, 8, 9], name='子图2'), row=1, col=2)

fig['layout']['annotations'] += (dict(
    x=0.5,
    y=-0.15,
    xref='paper',
    yref='paper',
    text='子图1',
    showarrow=False,
    font=dict(size=14)
),)

fig['layout']['annotations'] += (dict(
    x=0.5,
    y=-0.15,
    xref='paper',
    yref='paper',
    text='子图2',
    showarrow=False,
    font=dict(size=14)
),)

fig.show()