code: def returnOrderBook(self, currencyPair='all', depth='50'):
          
          return self._public('returnOrderBook', currencyPair=currencyPair,
                              depth=depth)
docs: Returns the order book for a given market, as well as a sequence
          number for use with the Push API and an indicator specifying whether
          the market is frozen. You may set currencyPair to "all" to get the
          order books of all markets.