public function setLowerBound($lowerBound)
    {
        if (is_float($lowerBound) || is_double($lowerBound) || (is_bool($lowerBound) && $lowerBound === false)) {
            $this->lowerBound = $lowerBound;
        } else {
            $msg = "The 'lowerBound' attribute must be a float or false, '" . gettype($lowerBound) . "' given.";
            throw new InvalidArgumentException($msg);
        }
    }