Importing attributes failed on \Brevo\Client\Model\CreateContact()

[draghetto84]

When I put attributes on CreateContact instance they're skipped and not imported.
Following my partial code:

$attribs = new \stdClass();
$attribs->FNAME = "Roger";
$attribs->LNAME = "White";

$createContact = new \Brevo\Client\Model\CreateContact();
$createContact->setEmail('[email protected]');
$createContact->setListIds([2]);
$createContact->setAttributes($attribs);
$createContact->setUpdateEnabled (true);

try {
$result = $apiInstance->createContact($createContact);
print_r($result);
} catch (Exception $e) {
print_r($e);
echo 'Exception when calling ContactsApi->createContact: ', $e->getMessage(), PHP_EOL;
}

the contact creation was successfully but without attributes. I only see the email in Brevo dashboard.