Pre format rules ignored - CI4 Validation

Hi Team,

If I apply any rule to CI4 Validation that returns string instead of boolean, that rule is skipped. No effect on data output / formatting.

Like this.

PHP Code:

$validation->setRules([
    'username' => 'trim|required',
    'password' => 'required|min_length[10]'
]); 


PHP Code:

$request->getPostGet('username'); // Username is not trimmed. 


This used to be working fine in CI3. How can I attain the same in CI4?