List users by role in dropdown

I need to write a function to load a list of users with a specific role and display the user’s first and last name.

I have read the official documentation here about the feature Choices Callback Feature in UM 2.1+
https://docs.ultimatemember.com/article/1539-choices-callback-feature-in-um-2-1
This does not help me

I need something like this but this doesn’t work

function my_dropdown_list() {
$args = array(
‘role’ => ‘MYROLE’
);
$users = get_users($args);
if( empty($users) )
return;
echo'<select>’;
foreach( $users as $user ){
echo ‘<option value=”‘.$user->data->first_name.'”>’.$user->data->last_name.'</option>’;
}
echo'</select>’;
}

Someone can help me please?
Regards
Lion