python-customuser模型不返回用户名

我有一个自定义模型

class customuser(AbstractUser):
    # additional fields    
    def __str__(self):
        return self.username

我有另一个模型，它成为这个模型的外键

class bfs_support_ticket_model(models.Model):
    ticket_created_by = models.ForeignKey(customuser, on_delete = models.CASCADE)

为什么Django不呈现表单的用户名，而是正确地呈现或返回所有地方的用户名？

class ticket_edit_form(ticket_create_form):

    # ticket_created_by = forms.CharField(widget=forms.TextInput(attrs={'class' : 'form-control', 'readonly' : True})) # does not work in this way

    def __init__(self, *args, **kwargs):
        super(ticket_edit_form,self).__init__(*args, **kwargs)
        # self.fields['ticket_created_by'].disabled = True
        self.fields['ticket_created_by'].widget = forms.TextInput(attrs={'class' : 'form-control', 'readonly' : True}) # doesnot work in this way too

    class Meta:
        model=bfs_support_ticket_model
        exclude=['ticket_last_updated_by']

当形式被呈现时，它只是打印 customuser.id 而不是 customuser.username 。

但是当没有初始化表单时，它会正确地返回 customuser.username 。

即何时

class ticket_edit_form(ticket_create_form):

    def __init__(self, *args, **kwargs):
        super(ticket_edit_form,self).__init__(*args, **kwargs)
        self.fields['ticket_created_by'].disabled = True # only this line present it renders customuser.username


    class Meta:
        model=bfs_support_ticket_model
        exclude=['ticket_last_updated_by']

请帮帮我，我哪里出错了

编辑：为什么

self.fields['ticket_created_by'].disabled = True # prints username

当

self.fields['ticket_created_by'].widget = forms.TextInput(attrs={'class' : 'form-control', 'readonly' : True}) # this doesn't