src/filters/auth/AuthMethod.php
protected function isOptional($action) {
        $id = $this->getActionId($action);
        return in_array($id, $this->optional, true);
    }
protected function isOptional($action) {
        $id = $this->getActionId($action);
        return in_array($id, $this->optional, true);
    }
Checks, whether the $action is optional

@param Action $action
@return boolean
@see optional
@since 2.0.7