КОНСТРУКЦИЯ №1 - не проходит тесты
class CashCalculator(Calculator):
    RUB_RATE = 1.00
    USD_RATE = 75.00
    EURO_RATE = 85.00
    RATES = {
            'rub': ['руб', RUB_RATE],
            'usd': ['USD', USD_RATE],
            'eur': ['Euro', EURO_RATE]
        }

КОНСТРУКЦИЯ №2 - проходит тесты
class CashCalculator(Calculator):
    RUB_RATE = 1.00
    USD_RATE = 75.00
    EURO_RATE = 85.00

    def get_today_cash_remained(self, currency):
        rates = {
            'rub': ['руб', self.RUB_RATE],
            'usd': ['USD', self.USD_RATE],
            'eur': ['Euro', self.EURO_RATE]
        }