Function contract 

fn contract(
    trade: El<'_, '_>,
    cds: El<'_, '_>,
    trade_date: NaiveDate,
    exercised_after: Option<NaiveDate>,
    ctx: &Context<'_>,
) -> Result<(AnyInstrument, Vec<AnyInstrument>), FpmlError>

A creditDefaultSwap as the contract it is, with its initial payment.