public function filterBy(string $className) : FluentIterable
    {
        return self::from(Iterables::filterBy($this, $className));
    }
public function filterBy(string $className) : FluentIterable
    {
        return self::from(Iterables::filterBy($this, $className));
    }
Returns the elements from this fluent iterable that are instances of class className.

@param string $className
@return FluentIterable