Spatie\MediaLibrary\Conversion\Conversion::setFormat PHP Method

    public function setFormat(string $format)
    {
        $validFormats = ['jpg', 'png', 'gif', 'src'];
        if (!in_array($format, $validFormats)) {
            throw InvalidConversionParameter::invalidFormat($format, $validFormats);
        }
        $this->setManipulationParameter('fm', $format);
        return $this;
    }