class My_Custom_Module extends myCRED_Hook {

    public function __construct() {
        parent::__construct(
            'My_Custom_Module',
            array(
                'module_name'  => 'custom',
                'defaults'     => array(
                    'field_name' => '',
                ),
                'register'     => false,
                'add_to_core'  => true
            )
        );
    }

    public function after_general_settings() {
        echo '<div class="custom-settings">Custom settings output.</div>';
    }

    public function sanitize_extra_settings($new_data, $data, $core) {
        if (isset($data['custom']['field_name'])) {
            $new_data['custom']['field_name'] = sanitize_text_field($data['custom']['field_name']);
        }
        return $new_data;
    }
}