public function invert($getClone = false)
{
$logMess = 'Invert sign';
if ($this->_value > 0) {
$newValue = -1 * $this->_value;
} elseif ($this->_value < 0) {
$newValue = abs($this->_value);
} else {
$newValue = $this->_value;
}
return $this->_modifer($newValue, $logMess, $getClone);
}