Connect two dropdown

Hello, i’m new in dash i saw lot of example of connect 2 dropdown but i still dont know how i can slove my problem,
i have to create to save the options selected in the dropdown to create a df with just the features selected from the dropdown.

i d’ont know how to create it (update_output_2 is the function that im trying create)

test is a empty div in the layout !

@app.callback(Output('display-data-table','children'),
              [Input('data-storage','children')])
def update_data_table(input_data):
    if input_data is not None:
        print(input_data)
        dff = pd.read_json(input_data[0],orient='split')
        return html.Div([
            dash_table.DataTable(
                data=dff.to_dict('records'),
                columns=[{'name': i, 'id': i} for i in dff.columns],
                style_table={'overflowX': 'scroll',
                             'maxHeight': '350px',
                             'overflowY': 'scroll'

                             },
                style_cell={
                    'minWidth': '100px',
                    'text-align': 'center',
                    'width': '30%'
                }
            ),

            html.Hr(),  # horizontal line

            dcc.Dropdown(
                id='dd_variables2',
                style={
                    'width': '99%',
                    'margin': '5px'
                },
                options=[{'label': i, 'value': i} for i in dff.keys()],
                value=dff.columns[0],
                multi=True
            ),
            
        ])
    
    
@app.callback(Output('test','children'),
              [Input('display-data-table','children')])

def update_output_2(input_data,value):
    
    dff = pd.read_json(input_data[0],orient='split')

    df.loc[df[].isin(some_values)]
    
    return  dash_table.DataTable(
                data=dff2.to_dict('records'),
                columns=[{'name': i, 'id': i} for i in dff2.columns],
                style_table={'overflowX': 'scroll',
                             'maxHeight': '350px',
                             'overflowY': 'scroll'

                             },
                style_cell={
                    'minWidth': '100px',
                    'text-align': 'center',
                    'width': '30%'
                }
            ),


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

Thank you for the help