public function getRoundCode($roundId)
    {
        $this->_ensureRounds();
        $roundCode = null;

        if (array_key_exists($roundId, $this->_rounds) && array_key_exists('gro_code', $this->_rounds[$roundId])) {
            $roundCode = $this->_rounds[$roundId]['gro_code'];
        }

        return $roundCode;
    }