Mockery\Container::getKeyOfDemeterMockFor PHP Method

    public function getKeyOfDemeterMockFor($method)
    {
        $keys = array_keys($this->_mocks);
        $match = preg_grep("/__demeter_{$method}\$/", $keys);
        if (count($match) == 1) {
            $res = array_values($match);
            if (count($res) > 0) {
                return $res[0];
            }
        }
        return null;
    }