private AnnuityDefinition<? extends PaymentDefinition> getOISLeg(final OISLegConvention convention, final SwapNode swapNode, final boolean isPayer,
final boolean isMarketDataSpread) {
final OvernightIndexConvention indexConvention = (OvernightIndexConvention) _conventionSource.getConvention(convention.getOvernightIndexConvention());
final Currency currency = indexConvention.getCurrency();
final DayCount dayCount = indexConvention.getDayCount();
final int publicationLag = indexConvention.getPublicationLag();
final Calendar calendar = CalendarUtils.getCalendar(_regionSource, _holidaySource, indexConvention.getRegionCalendar());
final int spotLagLeg = convention.getSettlementDays();
final ZonedDateTime spotDateLeg = ScheduleCalculator.getAdjustedDate(_valuationTime, spotLagLeg, calendar);
final Period maturityTenor = swapNode.getMaturityTenor().getPeriod();