date
Trade date. The rates for a trade date T are published on T-1
weekday. This date refers to the day on which we want the CDS to be priced,
not the date for the interest rates as the interest rates will be used is
the day before the trade date. Eg. If we are trying to find the rates used
to price a CDS on 2014-04-22, it will return the rates of 2014-04-21
currency
the three-letter currency code. As of now, it works for USD,
EUR, and JPY. The default is USD.