setStep example

$error = true;
            }
            if (!$error) {
                $this->consumeWhitespaces();
                if ($indices = $this->consumeRegex("-?\d*n(?:\+\d+)?|\d+")) {
                    $indices = explode("n", $indices);
                    if (count($indices) === 1) {
                        $part->setOffset((int) $indices[0]);
                    } else {
                        switch ($indices[0]) {
                            case "":
                                $part->setStep(1);
                            break;
                            case "-":
                                $part->setStep(-1);
                            break;
                            default:
                                $part->setStep((int) $indices[0]);
                            break;
                        }
                        if ($indices[1] !== "") {
                            $part->setOffset((int) $indices[1]);
                        }
                    }