ModelForm中缺少ID字段

Question

我正在使用DjangoCrispyForms，并且为我的ModelForm模型创建了一个User。
在Meta类中，我以表格的形式注册了我想要拥有的字段，其中之一是User的id。
问题是此id字段没有出现在表单中，我不得不手动将这样的字段添加到表单类中。当我想将更改保存到数据库并且需要从id中提取cleaned_data时，它变得更加复杂。

class EditUserForm(forms.ModelForm):
    id = forms.IntegerField() # needed to add this

    def __init__(self, *args, **kwargs):
        super(EditUserForm, self).__init__(*args, **kwargs)
        self.helper = FormHelper(self)

        self.fields['id'].widget = HiddenInput()

        self.helper.layout = Layout(
            Fieldset(
                'Edit user',
                'username',
                'first_name',
                'last_name',
                'email',
                'is_superuser',
                'id'
            ),
            ButtonHolder(
                Submit('submit', 'Save')
            ))

    def clean(self):
        username = self.cleaned_data.get('username')
        email = self.cleaned_data.get('email')
        if len(User.objects.filter(username=username)) > 1:
            self.add_error('username', 'Username is taken.')
        if len(User.objects.filter(email=email)) > 1:
            self.add_error('email', 'Account with this email exists')
        return self.cleaned_data

    def save(self, commit=True):
        instance = super(EditUserForm, self).save(commit=False)
        data_id = self.cleaned_data.get('id') # need to get this from data
        instance.id = data_id # and set id for instance
        if commit:
            instance.save()
        return instance

    class Meta:
        model = User
        fields = ['id', 'username', 'first_name', 'last_name', 'email', 'is_superuser'] # here we can see that id is actually present in fields

我错过了什么吗？应该是吗？