usecasper_types::{account::AccountHash,system::mint::Error, URef,U512};/// Provides functionality of a system module.
pubtraitSystemProvider{/// Records a transfer.
fnrecord_transfer(&mutself,
maybe_to:Option<AccountHash>,
source: URef,
target: URef,
amount: U512,
id:Option<u64>,
)->Result<(), Error>;}