protected function mergeDuplicates(array $line)
    {
        $values = [];

        $i = 0;
        foreach ($this->columnHeaders as $count) {
            if (1 === $count) {
                $values[] = $line[$i];
            } else {
                $values[] = array_slice($line, $i, $count);
            }

            $i += $count;
        }

        return $values;
    }