public function setGroupId($group_id)
    {
        if ($group_id instanceof GroupId) {
            $this->group_id = $group_id->getGroupId();
        } else {
            if (!is_int($group_id)) {
                throw new TypeException(
                    '$group_id must be an instance of Twilio SendGrid\Mail\GroupId or of type int.'
                );
            }
            $this->group_id = new GroupId($group_id);
        }
        return;
    }