docs: def get_xchange_rate(self, pairs, items=None):
          """Retrieves currency exchange rate data for given pair(s). 
          Accepts both where pair='eurusd, gbpusd' and where pair in ('eurusd', 'gpbusd, usdaud')
          """
          response = self.select('yahoo.finance.xchange', items).where(['pair', 'in', pairs])
          return response