Register the backends specified in Meta.backends with the admin.

def register_seo_admin(admin_site, metadata_class):
    """Register the backends specified in Meta.backends with the admin."""

    if metadata_class._meta.use_sites:
        path_admin = SitePathMetadataAdmin
        model_instance_admin = SiteModelInstanceMetadataAdmin
        model_admin = SiteModelMetadataAdmin
        view_admin = SiteViewMetadataAdmin
    else:
        path_admin = PathMetadataAdmin
        model_instance_admin = ModelInstanceMetadataAdmin
        model_admin = ModelMetadataAdmin
        view_admin = ViewMetadataAdmin

    def get_list_display():
        return tuple(
            name for name, obj in metadata_class._meta.elements.items()
            if obj.editable)

    backends = metadata_class._meta.backends

    if 'model' in backends:
        class ModelAdmin(model_admin):
            form = get_model_form(metadata_class)
            list_display = model_admin.list_display + get_list_display()

        _register_admin(admin_site, metadata_class._meta.get_model('model'),
                        ModelAdmin)

    if 'view' in backends:
        class ViewAdmin(view_admin):
            form = get_view_form(metadata_class)
            list_display = view_admin.list_display + get_list_display()

        _register_admin(admin_site, metadata_class._meta.get_model('view'),
                        ViewAdmin)

    if 'path' in backends:
        class PathAdmin(path_admin):
            form = get_path_form(metadata_class)
            list_display = path_admin.list_display + get_list_display()

        _register_admin(admin_site, metadata_class._meta.get_model('path'),
                        PathAdmin)

    if 'modelinstance' in backends:
        class ModelInstanceAdmin(model_instance_admin):
            form = get_modelinstance_form(metadata_class)
            list_display = (model_instance_admin.list_display +
                            get_list_display())

        _register_admin(admin_site,
                        metadata_class._meta.get_model('modelinstance'),
                        ModelInstanceAdmin)