@classmethod
def get_commissions(cls, contract_values, turnover, **kwargs):
    """
        Return a DataFrame of commissions as percentages of account equity.
        """
    cost_per_contract = (cls.BROKER_COMMISSION_PER_CONTRACT + cls.
        EXCHANGE_FEE_PER_CONTRACT + cls.CARRYING_FEE_PER_CONTRACT)
    commission_rates = float(cost_per_contract) / contract_values
    commissions = commission_rates * turnover
    return commissions
