some validation checks before doing anything

def validate_currency(*currencies):
	""" some validation checks before doing anything """
	validated_currency = []
	if not currencies:
		raise CurrencyException('My function need something to run, duh')
	for currency in currencies:
		currency = currency.upper()
		if not isinstance(currency, str):
			raise TypeError('Currency code should be a string: ' + repr(currency))
		if currency not in _currencies:
			raise CurrencyException('Currency code not found: ' + repr(currency))
		validated_currency.append(currency)
	return validated_currency[0] if len(validated_currency) == 1 else validated_currency