SortableHiddenMixin module 'nested_admin' has no attribute 'SortableHiddenMixin'

[maxi-89]

HI, im getting this error ...

line 61, in __getattr__ return ModuleType.__getattribute__(self, name) AttributeError: module 'nested_admin' has no attribute 'SortableHiddenMixin

here my code:

`class ReportSectionFieldInline(nested_admin.SortableHiddenMixin, nested_admin.NestedTabularInline):
model = ReportSectionField
extra = 0
classes = ['collapse']

class ReportSectionInline(nested_admin.SortableHiddenMixin, nested_admin.NestedTabularInline):
model = ReportSection
inlines = [ReportSectionFieldInline]
extra = 0
classes = ['secciones-informe']

class Media:
    css = {
        "all": ("admin/css/reportsection.css",)
    }

class ReportAdmin(nested_admin.NestedModelAdmin):
list_display = ('id', 'description', 'type_report', 'modulo', 'active',)
search_fields = ('description', 'type_report',)
list_filter = ('type_report', 'active',)

inlines = [ReportSectionInline]`

ty!