public function matchOne(array $contentConditions, array $versionConditions = array(), $sort = array(), $offset = 0)
    {
        $results = $this->match($contentConditions, $versionConditions, $sort, $offset, 2);
        $count = count($results);
        if ($count !== 1) {
            throw new InvalidMatchResultsNumberException("Found $count " . $this->returns . " when expected exactly only one to match the conditions");
        }
        return reset($results);
    }