如何通过Dash回调从dataframe中获取计数

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output
import pandas as pd

data = pd.read_csv('data.csv')  # 假设数据保存在data.csv文件中
df = pd.DataFrame(data)

app = dash.Dash(__name__)

app.layout = html.Div([
    dcc.Input(id='input', value='', type='text'),
    html.Div(id='output')
])

@app.callback(
    Output('output', 'children'),
    [Input('input', 'value')]
)
def get_count(input_value):
    count = df[input_value].value_counts()
    return count.to_string()

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