public function addMime(string $sMime, array $aExtensions): self
    {
        $this->updateMap(static::$aMapMimeToExtensions, $sMime, $aExtensions);
        foreach ($aExtensions as $sExtension) {
            $this->updateMap(static::$aMapExtensionToMimes, $sExtension, [$sMime]);
        }
        return $this;
    }