I was also facing the same issue every class needs models.Model and issue should get sorted -

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]