[Python] displaying mean value using bar command and dash framework

my little project is following : we have a small database, in which information about car, their prices and country are presented, user selects any country and based on this one, mean value for given country is selected, here is my code :

from sqlalchemy import create_engine,text
#pip install pandas psycopg2-binary SQLAlchemy
from dash import Dash, html, dcc, callback, Output, Input
import plotly.express as px
import pandas as pd
app = Dash()

# Requires Dash 2.17.0 or later
app.layout = [
html.H1(children='Title of Dash App', style={'textAlign':'center'}),
dcc.Dropdown(["France","Germany","Italy"], 'France', id='dropdown-selection'),
dcc.Graph(id='graph-content')
]

@callback(
Output('graph-content', 'figure'),
Input('dropdown-selection', 'value')
)
def update_graph(value):
country = (value,)
engine = create_engine('postgresql+psycopg2://postgresassword@localhost/postgres')
data = pd.read_sql(con=engine, sql='select * from CAR where country in (%s)', params=country)
print(data)

return px.bar(data_frame=data.groupby([value]).mean().reset_index(), x='price', y=value)

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






# con =engine.connect()
# con.execute(text('select * from leptop'))


when i run code, i am getting following result :

could you tell me please exactly where am i making mistake? please give me little hint

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