在Python Dash中显示matplotlib和seaborn图不起作用。我们怎么才能让它工作呢？

import dash
import dash_core_components as dcc
import dash_html_components as html
import matplotlib.pyplot as plt
import seaborn as sns

app = dash.Dash(__name__)

app.layout = html.Div([
    dcc.Graph(id='graph')
])

@app.callback(
    dash.dependencies.Output('graph', 'figure'),
    []
)
def update_graph():
    # 生成matplotlib和seaborn图表
    fig, ax = plt.subplots()
    sns.set()
    sns.scatterplot(x=[1, 2, 3], y=[4, 5, 6], ax=ax)
    
    return fig

if __name__ == '__main__':
    app.run_server(debug=True)