code: def total_regular_pixels_from_mask(mask):
      
  
      total_regular_pixels = 0
  
      for y in range(mask.shape[0]):
          for x in range(mask.shape[1]):
              if not mask[y, x]:
                  total_regular_pixels += 1
  
      return total_regular_pixels
docs: Compute the total number of unmasked regular pixels in a masks.