问 在model_or_iterable: TypeError：'type‘对象中查看模型错误寄存器是不可迭代的

from django.db import models
# Create your models here.
class Post(models.Model):
    text = models.TextField()
    def __str__(self):
        return self.text[:50]
POWER_CHOICES= (('O', 'ON'),
                ('F','OFF')
STATE_CHOICES =(('AV','Available'),
               ('U','In Use '),
               ('NU','Do Not Use')                
class Device(models.Model):
   name = models.CharField(unique=True,max_length=50 )
   ipaddress=models.ForeignKey('Ipaddress', on_delete=models.CASCADE,)
   devicetype= models.ForeignKey('DeviceType', on_delete=models.CASCADE)
   model= models.ForeignKey('DeviceModel', on_delete=models.CASCADE)
   description= models.TextField(max_length=400)
   location= models.ForeignKey('Location', on_delete=models.CASCADE)
   group= models.ForeignKey('DeviceGroup', on_delete=models.CASCADE)
   managment= models.CharField(max_length=100)
   power= models.CharField(max_length=6, choices=POWER_CHOICES)
   offtime= models.CharField(max_length=30)
   state= models.CharField(max_length=10, choices=STATE_CHOICES)
   user= models.CharField(max_length=100)
#   department= models.ForeignKey('Department',on_delete=models.CASCADE)
   comments= models.CharField(max_length=200)
   def __unicode__(self):
        return self.name[:50]
class DeviceType(models.Model):
    name= models.CharField(max_length=100, unique=True)
    def __unicode__(self):
        return self.name[:50]
class DeviceModel(models.Model):
    name= models.CharField(max_length=100, unique=True)
    def __unicode__(self):
        return self.name[:50]
class Ipaddress(models.Model):
    address=models.CharField(max_length=20, unique=True)
    owner=models.CharField(max_length=200)
    loation=models.CharField(max_length=200)
    note =models.TextField()
    def __unicode__(self):
        return self.address[:50]
class Department:
    name= models.CharField(max_length=100, unique=True)
    def __unicode__(self):
        return self.name[:50] 
class DeviceGroup:
    name= models.CharField(max_length=100, unique=True)
    def __unicode__(self):
        return self.name[:50] 
class Location:
    description= models.CharField(max_length=100, unique=True)
    def __unicode__(self):
        return self.description[:50] 

from django.contrib import admin
from pages.models import Post, Device, DeviceType, DeviceModel, Ipaddress, DeviceGroup, Location
admin.site.register(Post)
admin.site.register(Device)
admin.site.register(DeviceType)
admin.site.register(DeviceModel)
admin.site.register(Ipaddress)
#admin.site.register(Department)
admin.site.register(DeviceGroup)
admin.site.register(Location)

...
File "C:\Users\mohiuddin_rana\labmcproject\pages\admin.py", line 10, in <module>
    admin.site.register(DeviceGroup)
  File "C:\Users\mohiuddin_rana\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\contrib\admin\sites.py", line 102, in register
    for model in model_or_iterable:
TypeError: 'type' object is not iterable