当选项下拉字段不包含任何数据时，如何在Django的管理页面中禁用添加权限？

from django.contrib import admin
from django import forms

class MyModelForm(forms.ModelForm):
    def get_form(self, request, obj=None, **kwargs):
        form = super().get_form(request, obj, **kwargs)
        if not form.fields['your_field_name'].choices:
            form.fields['your_field_name'].widget.attrs['disabled'] = True
        return form

from .models import YourModel

@admin.register(YourModel)
class YourModelAdmin(admin.ModelAdmin):
    form = MyModelForm