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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add(assetclass: int, symbol: str):
 """ Add a stock to an asset class """

    assert isinstance(symbol, str)
    assert isinstance(assetclass, int)

    symbol = symbol.upper()
    app = AppAggregate()
    new_item = app.add_stock_to_class(assetclass, symbol)
    print(f"Record added: {new_item}.")