How to use the wagtailvideos.models.VideoQuality function in wagtailvideos

return {
                VideoQuality.lowest: '50',
                VideoQuality.default: '22',
                VideoQuality.highest: '4'
            }[quality]
        elif self is MediaFormats.mp4:
            return {
                VideoQuality.lowest: '28',
                VideoQuality.default: '24',
                VideoQuality.highest: '18'
            }[quality]
        elif self is MediaFormats.ogg:
            return {
                VideoQuality.lowest: '5',
                VideoQuality.default: '7',
                VideoQuality.highest: '9'
            }[quality]

def get_quality_param(self, quality):
        if self is MediaFormats.webm:
            return {
                VideoQuality.lowest: '50',
                VideoQuality.default: '22',
                VideoQuality.highest: '4'
            }[quality]
        elif self is MediaFormats.mp4:
            return {
                VideoQuality.lowest: '28',
                VideoQuality.default: '24',
                VideoQuality.highest: '18'
            }[quality]
        elif self is MediaFormats.ogg:
            return {
                VideoQuality.lowest: '5',
                VideoQuality.default: '7',
                VideoQuality.highest: '9'
            }[quality]

form=BaseVideoForm,
        fields=fields,
        formfield_callback=formfield_for_dbfield,
        # set the 'file' widget to a FileInput rather than the default ClearableFileInput
        # so that when editing, we don't get the 'currently: ...' banner which is
        # a bit pointless here
        widgets={
            'tags': widgets.AdminTagWidget,
            'file': forms.FileInput(),
            'thumbnail': forms.FileInput(),
        })


class VideoTranscodeAdminForm(forms.Form):
    media_format = EnumField(MediaFormats)
    quality = EnumField(VideoQuality)

    def __init__(self, video, data=None, **kwargs):
        super(VideoTranscodeAdminForm, self).__init__(data=data, **kwargs)
        self.video = video

    def save(self):
        media_format = self.cleaned_data['media_format']
        quality = self.cleaned_data['quality']
        self.video.do_transcode(media_format, quality)


GroupVideoPermissionFormSet = collection_member_permission_formset_factory(
    Video,
    [
        ('add_video', _("Add"), _("Add/edit images you own")),
        ('change_video', _("Edit"), _("Edit any video")),

with get_local_file(instance.file) as file_path:
            if has_changed or instance.thumbnail is None:
                instance.thumbnail = ffmpeg.get_thumbnail(file_path)

            if has_changed or instance.duration is None:
                instance.duration = ffmpeg.get_duration(file_path)

    instance.file_size = instance.file.size
    instance._from_signal = True
    instance.save()
    del instance._from_signal


class AbstractVideoTranscode(models.Model):
    media_format = EnumChoiceField(MediaFormats)
    quality = EnumChoiceField(VideoQuality, default=VideoQuality.default)
    processing = models.BooleanField(default=False)
    file = models.FileField(null=True, blank=True, verbose_name=_('file'),
                            upload_to=get_upload_to)
    error_message = models.TextField(blank=True)

    @property
    def url(self):
        return self.file.url

    def get_upload_to(self, filename):
        folder_name = 'video_transcodes'
        filename = self.file.field.storage.get_valid_name(filename)
        return os.path.join(folder_name, filename)

    class Meta:
        abstract = True

if self is MediaFormats.webm:
            return {
                VideoQuality.lowest: '50',
                VideoQuality.default: '22',
                VideoQuality.highest: '4'
            }[quality]
        elif self is MediaFormats.mp4:
            return {
                VideoQuality.lowest: '28',
                VideoQuality.default: '24',
                VideoQuality.highest: '18'
            }[quality]
        elif self is MediaFormats.ogg:
            return {
                VideoQuality.lowest: '5',
                VideoQuality.default: '7',
                VideoQuality.highest: '9'
            }[quality]