prevent duplicate form submission by user in Contact form 7

Have a look at this example: https://cfdbplugin.com/?page_id=904

I looked in to this but I am not sure how to implement this can you help me how to implement along with this code and where should I place this code

if (is_user_logged_in()) {
$current_user = wp_get_current_user(); // WP_User object
$user = $current_user->user_login;
$atts[‘filter’] = “$fieldName=$fieldValue&&Submitted Login=$user”;
}

I think all you need to do is change this line:

$fieldName = 'email_123'; // Change to your form's unique field name

to:

$fieldName = 'Submitted Login'; // Change to your form's unique field name

But beware that this check will apply to all of your forms, due to the limitation in CF7 (where the field validation doesn’t tell you want form it is associated with)

Thanks Michael for your prompt reply,

in which file I should Implement this code?

Follow the directions in the example