@SuppressWarnings("unchecked")
    public static <D> SetPath<D, SimpleExpression<D>> $(Set<D> arg) {
        final Object current = aliasFactory.getCurrentAndReset();
        if (arg instanceof SetPath) {
            return (SetPath<D, SimpleExpression<D>>) arg; //NOSONAR
        } else if (arg instanceof ManagedObject) {
            return (SetPath<D, SimpleExpression<D>>) ((ManagedObject) arg).__mappedPath();
        } else {
            return (SetPath<D, SimpleExpression<D>>) current;
        }
    }
Convert the given alias to an expression

@param arg alias
@param <D>
@return expression
querydsl-core/src/main/java/com/querydsl/core/alias/Alias.java