django - 「SimpleHistoryAdmin」には属性 _meta の問題がありません

Question

django-simple-history をインストール
しましたが、機能しません。
私はpython manage.py makemigrationsを試し
ましたが、エラーの下でペースを上げました。like AttributeError: type object 'SimpleHistoryAdmin' has no attribute '_meta' django-admin で履歴を見たいです。

どうしたの？？？？？

Traceback (most recent call last):
    class AccountClassificationAdmin(admin.ModelAdmin):
  File "/root/miniconda3/envs/gdaj/lib/python3.9/site-packages/django/contrib/admin/decorators.py", line 100, in _model_admin_wrapper
    admin_site.register(models, admin_class=admin_class)
  File "/root/miniconda3/envs/gdaj/lib/python3.9/site-packages/django/contrib/admin/sites.py", line 113, in register
    if model._meta.abstract:
AttributeError: type object 'SimpleHistoryAdmin' has no attribute '_meta'

# settings.py

i added 
'simple_history', at installed_app
'simple_history.middleware.HistoryRequestMiddleware', at middleware

# models.py

class PayHistory(TimeStampedModel):
    package_patient = models.CharField(max_length=10, null=False)
    package_classification = models.CharField(max_length=10, null=False)
    history = HistoricalRecords()

class PayHistoryChange(TimeStampedModel):
    payhistory = models.ForeignKey(PayHistory, on_delete=models.CASCADE, null=False)
    history = HistoricalRecords()

# admin.py
@admin.register(PayHistory)
class PayHistoryAdmin(SimpleHistoryAdmin):
    list_display = (
        "package_patient",
        "package_classification"
    )

i tried admin.site.register(PayHistory, PayHistoryAdmin)
but it's also not working