How to use the wagtailmedia.models.get_media_model function in wagtailmedia

def edit(request, media_id):
    Media = get_media_model()
    MediaForm = get_media_form(Media)

    media = get_object_or_404(Media, id=media_id)

    if not permission_policy.user_has_permission_for_instance(request.user, 'change', media):
        return permission_denied(request)

    if request.POST:
        original_file = media.file
        form = MediaForm(request.POST, request.FILES, instance=media, user=request.user)
        if form.is_valid():
            if 'file' in form.changed_data:
                # if providing a new media file, delete the old one.
                # NB Doing this via original_file.delete() clears the file field,
                # which definitely isn't what we want...
                original_file.storage.delete(original_file.name)

def index(request):
    Media = get_media_model()

    # Get media files (filtered by user permission)
    media = permission_policy.instances_user_has_any_permission_for(
        request.user, ['change', 'delete']
    )

    # Ordering
    if 'ordering' in request.GET and request.GET['ordering'] in ['title', '-created_at']:
        ordering = request.GET['ordering']
    else:
        ordering = '-created_at'
    media = media.order_by(ordering)

    # Filter by collection
    current_collection = None
    collection_id = request.GET.get('collection_id')

def usage(request, media_id):
    Media = get_media_model()
    media = get_object_or_404(Media, id=media_id)

    paginator, used_by = paginate(request, media.get_usage())

    return render(request, "wagtailmedia/media/usage.html", {
        'media': media,
        'used_by': used_by
    })

def get_context(self):
        return {
            'total_media': get_media_model().objects.count(),
        }

def describe_collection_media(collection):
    media_count = get_media_model().objects.filter(collection=collection).count()
    if media_count:
        url = reverse('wagtailmedia:index') + ('?collection_id=%d' % collection.id)
        return {
            'count': media_count,
            'count_text': ungettext(
                "%(count)s media file",
                "%(count)s media files",
                media_count
            ) % {'count': media_count},
            'url': url,
        }

def __init__(self, **kwargs):
        super(AdminMediaChooser, self).__init__(**kwargs)
        self.media_model = get_media_model()

def delete(request, media_id):
    Media = get_media_model()
    media = get_object_or_404(Media, id=media_id)

    if not permission_policy.user_has_permission_for_instance(request.user, 'delete', media):
        return permission_denied(request)

    if request.POST:
        media.delete()
        messages.success(request, _("Media file '{0}' deleted.").format(media.title))
        return redirect('wagtailmedia:index')

    return render(request, "wagtailmedia/media/confirm_delete.html", {
        'media': media,
    })

def chooser(request):
    Media = get_media_model()

    media_files = []

    q = None
    is_searching = False
    if 'q' in request.GET or 'p' in request.GET or 'collection_id' in request.GET:
        media_files = Media.objects.all()

        collection_id = request.GET.get('collection_id')
        if collection_id:
            media_files = media_files.filter(collection=collection_id)

        searchform = SearchForm(request.GET)
        if searchform.is_valid():
            q = searchform.cleaned_data['q']

def media_chosen(request, media_id):
    media = get_object_or_404(get_media_model(), id=media_id)

    return render_modal_workflow(
        request, None, None,
        None,
        json_data={'step': 'media_chosen', 'result': get_media_json(media)}
    )

def target_model(self):
        from wagtailmedia.models import get_media_model
        return get_media_model()