is_unique issue on update

I have an issue when update an user with is_unique rule. 
I would like ignore email address if email is the same, otherwise the mail have to be check for haven't duplicates. 
How can i do? 

I have read here: https://codeigniter4.github.io/userguide...able-rules but something doesn't works.

PHP Code:

$rules = ([
        'email'    => [
          'label'  => 'Email',
          'rules'  => 'required|min_length[3]|max_length[50]|valid_email|is_unique[tbl_users.X,X,X]',
        ],
      ]); 


Thanks for help me.