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product.py

class Product(ExampleModel):
    name = Column(String, nullable=False)
    description = Column(Text)
    list_price = Column(Numeric)
    sell_price = Column(Numeric)
    variants = relationship('Variant', backref="product")


class Variant(ExampleModel):
    product_id = Column(ForeignKey('products.id'))
    inventory = relationship('Inventory')


class Inventory(ExampleModel):
    variant_id = Column(ForeignKey('variants.id'))
    available_to_sell = Column(Integer, nullable=False)