[Python] How to make a callback function that draws a graph with a python dash button works

I want to draw a graph when I press the python dash button. So I created a button called btn-run and a callback function called btn_run_click. However, a new plot is not drawn when the button is pressed. The code is attached below. Is there someone who can help?

import dash
from dash import Dash, dcc, html, Input, Output
import plotly.express as px
import pandas as pd

app = dash.Dash(__name__)

app.layout = html.Div([
html.Br(),
html.Button('start', id='btn-run', n_clicks=0,
style={'width':'150px','height':'30px'}),
dcc.Graph(id='main-plot', figure={}),
html.Br()
])

@app.callback(
Output('main-plot', 'children'),
Input('btn-run','n_clicks')
)
def btn_run_click(btn_run):

if btn_run == 0 : return
df = pd.DataFrame({
"Fruits":['Apples', 'Oranges', 'Bananas'],
"Amount":[4,3,6]
})

fig = px.bar(df, x = "Fruits", y = "Amount", barmode='group')
return dcc.Graph(figure=fig)

if __name__ == '__main__':
app.run_server(debug=False, port=8052)

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