protected function realGroup(
        $col,
        /*# sting */ $suffix = '',
        /*# bool */ $rawMode = false
    ) {
    
        if (is_array($col)) {
            $this->multipleGroup($col, $suffix);
        } else {
            $clause = &$this->getClause('GROUP BY');
            $part = [$col, $this->isRaw($col, $rawMode)];
            if (!empty($suffix)) {
                $part[] = $suffix;
            }
            $clause[] = $part;
        }
        return $this;
    }