public function attemptToFormatAccruedDigits()
    {
        foreach ($this->possibleFormats as $numberFormat) {
            $m = new Matcher($numberFormat->getPattern(), $this->nationalNumber);
            if ($m->matches()) {
                $nationalPrefixSeparatorsMatcher = new Matcher(self::$nationalPrefixSeparatorsPattern, $numberFormat->getNationalPrefixFormattingRule());
                $this->shouldAddSpaceAfterNationalPrefix = $nationalPrefixSeparatorsMatcher->find();
                $formattedNumber = $m->replaceAll($numberFormat->getFormat());
                return $this->appendNationalNumber($formattedNumber);
            }
        }
        return '';
    }