code: def normalise(self, to_currency):
          
          out = Money(currency=to_currency)
          for money in self._money_obs:
              out += converter.convert(money, to_currency)
          return Balance([out])
docs: Normalise this balance into a single currency
  
          Args:
              to_currency (str): Destination currency
  
          Returns:
              (Balance): A new balance object containing a single Money value in the specified currency