code: public static CurrencyFunction currency(String fieldName, @Nullable String currencyCode) {
  
  		Assert.hasText(fieldName, "FieldName for currency function must not be 'empty'.");
  		return currency(new SimpleField(fieldName), currencyCode);
  	}
docs: Create new {@link CurrencyFunction} using ISO-4217 currencyCode representing
  {@code currency(fieldname,currencyCode)}
  
  @param fieldName
  @param currencyCode
  @return