country = ChainedForeignKey(Country, chained_field='continent',
    chained_model_field='continent', show_all=False, auto_choose=True)
area = ChainedForeignKey(Area, chained_field='country', chained_model_field
    ='country')
city = models.CharField(max_length=50)
street = models.CharField(max_length=100)
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