protected function renderSeparator($spanLeft, $spanMid, $spanMidMid, $spanRight)
    {
        $separator = $spanLeft;
        foreach ($this->_columnWidths as $index => $rowSize) {
            if ($index !== 0) {
                $separator .= $spanMid;
            }
            $separator .= str_repeat($spanMidMid, $rowSize);
        }
        $separator .= $spanRight . "\n";
        return $separator;
    }