mint certain amount of underlying to dst address
redeem certain amount of dToken from dst address
redeem certain amount of underlying from dst address
return the most recent exchange rate, scaled by 1e18
return the total underlying token amount
return current liquidity of the underlying token
return the underlying token balance of the given account
return (decimals, exchangeRate, mintFeeRate, redeemFeeRate, totalUnderlying)
return fee, scaled by 1e18
return true if paused, false if not paused
return fee receiving address