The third-order super smoother low-pass butterworth filter (3 pole) is a classic J.F Ehlers indicator.
Function
I have found many places where the algorithms are not uniform and some are even wrong. So, I did some research and wrote a low pass filter that I think is correctly defined. This indicator is often used as one of the basic elements of other trading systems.
When you are using it, you need to enter the Period setting period.