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

def get_media_model():
    from django.conf import settings
    from django.apps import apps

    try:
        app_label, model_name = settings.WAGTAILMEDIA_MEDIA_MODEL.split('.')
    except AttributeError:
        return Media
    except ValueError:
        raise ImproperlyConfigured("WAGTAILMEDIA_MEDIA_MODEL must be of the form 'app_label.model_name'")

    media_model = apps.get_model(app_label, model_name)
    if media_model is None:
        raise ImproperlyConfigured(
            "WAGTAILMEDIA_MEDIA_MODEL refers to model '%s' that has not been installed" %
            settings.WAGTAILMEDIA_MEDIA_MODEL
        )
    return media_model

# and when only one collection exists, it will get hidden anyway.
        fields = list(fields) + ['collection']

    return modelform_factory(
        model,
        form=BaseMediaForm,
        fields=fields,
        widgets={
            'tags': widgets.AdminTagWidget,
            'file': forms.FileInput(),
            'thumbnail': forms.ClearableFileInput(),
        })


GroupMediaPermissionFormSet = collection_member_permission_formset_factory(
    Media,
    [
        ('add_media', _("Add"), _("Add/edit media you own")),
        ('change_media', _("Edit"), _("Edit any media")),
    ],
    'wagtailmedia/permissions/includes/media_permissions_formset.html'
)

@receiver(pre_delete, sender=Media)
def media_delete(sender, instance, **kwargs):
    # Pass false so FileField doesn't save the model.
    instance.file.delete(False)
    instance.thumbnail.delete(False)

from django.conf import settings
from django.contrib import admin

from wagtailmedia.models import Media

if hasattr(settings, 'WAGTAILMEDIA_MEDIA_MODEL') and settings.WAGTAILMEDIA_MEDIA_MODEL != 'wagtailmedia.Media':
    # This installation provides its own custom media class;
    # to avoid confusion, we won't expose the unused wagtailmedia.Media class
    # in the admin.
    pass
else:
    admin.site.register(Media)

from wagtail.core.permission_policies.collections import CollectionOwnershipPermissionPolicy

from wagtailmedia.models import Media, get_media_model

permission_policy = CollectionOwnershipPermissionPolicy(
    get_media_model(),
    auth_model=Media,
    owner_field_name='uploaded_by_user'
)