NameError：name＆＃39; RandomCharField＆＃39;未定义

Question

from django_extensions.db.fields import RandomCharField

class Product(models.Model):
    stock = RandomCharField(length=4, include_alpha=False)

  

NameError：name＆＃39; RandomCharField＆＃39;未定义

如何解决？