Campo de escolhas dinâmicas no Django Models

My models.py

SHOP1_CHOICES = (
    ('Food Court', 'Food Court'),
    ('KFC', 'KFC'),

)

SHOP2_CHOICES = (
    ('Sports Arena', 'Sports Arena'),
    ('Disco D', 'Disco D'),

)

SHOP3_CHOICES = (
    ('Bowling Arena', 'Bowling Arena'),
    ('Cinemax', 'Cinemax'),

)

class Feed(models.Model):
  gender = models.CharField(max_length=5, choices=GENDER_CHOICES, default='girl')
  name =models.CharField(max_length=25)
  shop=models.CharField(max_length=20)
  location=models.CharField(max_length=25, choices=SHOP1_CHOICES)

Aqui seFeed.shop == 'shop1' Eu quero carregarSHOP1_CHOICES emFeed.location. Atualmente, independentemente de qual loja, ele apenas exibe oSHOP1_CHOICES (sem surpresa) .Como posso implementá-lo? Estou preso, por favor me ajud

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