@classmethod
def set_default(cls, currency_code: str):
    """Set currency as base currency with value of 1.

        :param currency_code: Code of base currency
        """
    currency = cls.query.filter_by(code=currency_code).first()
    if currency is None:
        raise ValueError(f'Currency not found: {currency_code}')
    value = currency.value
    for c in cls.query.all():
        c.value /= value
