pub fn estimate_escrow_reward_rate<T, EscrowAnnuityInstance, EscrowRewardsApi, EscrowCurrency>(
account_id: AccountId<T>,
amount: Option<Balance>,
lock_time: Option<BlockNumber>
) -> Result<UnsignedFixedPoint, DispatchError>where
T: Config + Config<Currency = EscrowCurrency> + Config<EscrowAnnuityInstance, Currency = EscrowCurrency>,
EscrowAnnuityInstance: 'static,
EscrowRewardsApi: RewardsApi<(), AccountId<T>, Balance, CurrencyId = CurrencyId<T>>,
EscrowCurrency: Currency<<T as Config>::AccountId, Balance = Balance>,