Implement a "Average Image Filter" using Python standard libraries. You may not use any "instant" methods and must write the code from scratch. You also may not use CV2. You may use numpy and PIL if needed. This method must work on RGB images and the final result must be in RGB format.

Block size is up to the user.

An average filter simply takes the selected pixel and averages surrounding pixels in a matrix according to the block size. For example if the block size is 3x3, then from the center pixel: It must add up the left, right, top, bottom and diagonal. Then average them then assign it to the pixel. it does this on a loop for every pixel in the image to create a blur.