code: def _get_nadir_pixel(earth_mask, sector):
          
          if sector == FULL_DISC:
              logger.debug('Computing nadir pixel')
  
              # The earth is not centered in the image, compute bounding box
              # of the earth disc first
              rmin, rmax, cmin, cmax = bbox(earth_mask)
  
              # The nadir pixel is approximately at the centre of the earth disk
              nadir_row = rmin + (rmax - rmin) // 2
              nadir_col = cmin + (cmax - cmin) // 2
  
              return nadir_row, nadir_col
  
          return None, None
docs: Find the nadir pixel
  
          Args:
              earth_mask: Mask identifying earth and space pixels
              sector: Specifies the scanned sector
          Returns:
              nadir row, nadir column