public function setLastName($lastName = null)
    {
        if (($this->getMajorProtocolVersion() == null) ||
           ($this->getMajorProtocolVersion() == 1)) {
            require_once 'Zend/Gdata/App/VersionException.php';
            throw new Zend_Gdata_App_VersionException('The setLastName ' .
                ' method is only supported as of version 2 of the YouTube ' .
                'API.');
        } else {
            $this->_lastName = $lastName;
            return $this;
        }
    }