<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def as_currency(self, currency='USD', locale=LOCALE_OBJ, *args, **kwargs):
 """Format subset as currency :param currency: Currency :param locale: Babel locale for currency formatting :param subset: Pandas subset """

        f = Formatter(
            as_currency(currency=currency, locale=locale),
            args,
            kwargs
        )
        return self._add_formatter(f)