django 添加信息时，对外键设置条件

class CustomerForm(forms.ModelForm):
    class Meta:
        model = Customer
        #fields = '__all__'
        exclude=['sal_name','code']
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)


        #审核员只显示管理员用户
        self.fields['oa'].queryset=UserInfo.objects.filter(role=2)


        # 修改生成的input标签的样式
        for name, field in self.fields.items():
            field.widget.attrs = {"class": "form-control"}
    def clean_order_num(self):
        order_num = self.cleaned_data['order_num']
        exists=Customer.objects.exclude(id=self.instance.pk).filter(order_num=order_num).exists()
        if exists:
            raise ValidationError("当前订单号已存在")
        return order_num

上面的

#审核员只显示管理员用户

self.fields'oa'.queryset=UserInfo.objects.filter(role=2)