code: def get_rate(currency):
      
      source = get_rate_source()
      try:
          return Rate.objects.get(source=source, currency=currency).value
      except Rate.DoesNotExist:
          raise CurrencyConversionException(
              "Rate for %s in %s do not exists. "
              "Please run python manage.py update_rates" % (
                  currency, source.name))
docs: Returns the rate from the default currency to `currency`.