private function findTableChars(string $line) : ?array
    {
        $lineChar  = $line[0];
        $spaceChar = null;

        for ($i = 0; $i < strlen($line); $i++) {
            if ($line[$i] === $lineChar) {
                continue;
            }

            if ($spaceChar === null) {
                $spaceChar = $line[$i];

                continue;
            }

            if ($line[$i] !== $spaceChar) {
                return null;
            }
        }

        if ($spaceChar === null) {
            return null;
        }

        return [$lineChar, $spaceChar];
    }