I wanna resist id in serial number like 1,2,3・・・.I wrote codes to resist User data like,

```
from django.db import models
import uuid

# Create your models here.
def get_next():
    try:
        return Users.objects.latest('pk').increment_num + 1
    except:
        return 1

class Users(models.Model):
    id = models.UUIDField(primary_key=True, default=get_next, editable=False)
    sex = models.CharField(max_length=100, null=True, default=None)
    age = models.CharField(max_length=100, null=True, default=None)

```

But when I try to resist user's data,

> 
> django.core.exceptions.ValidationError: ["'1' is not a valid UUID."]
> 
> 
> 

error happens.
So I rewrote `id = models.IntegerField(primary_key=True, default=get_next)`, but if I resist multiple user's data, only id=1's data is remain and I cannot understand but other data was deleted. What is wrong in my code? How should I fix this?