public function removeNotReplacedChar($notReplaced)
    {
        if (empty($notReplaced)) {
            throw new \Exception('Not replaced character cannot be null.');
        }
        if (is_array($notReplaced)) {
            foreach ($notReplaced as $n) {
                $this->removeNotReplacedChar($n);
            }
        } else {
            if (! in_array($notReplaced, $this->getNotReplacedChars())) {
                throw new \Exception("Not replaced character '$notReplaced' is not in array.");
            }
            $newArray = array();
            foreach ($this->_notReplacedChars as $n) {
                if ($n != $notReplaced) {
                    $newArray[] = $n;
                }
                $this->_notReplacedChars = $newArray;
            }
        }
        return $this;
    }