code: def _validate_jp2_colr(self, boxes):
          
          lst = [box for box in boxes if box.box_id == 'jp2h']
          jp2h = lst[0]
          for colr in [box for box in jp2h.box if box.box_id == 'colr']:
              if colr.approximation != 0:
                  msg = ("A JP2 colr box cannot have a non-zero approximation "
                         "field.")
                  raise IOError(msg)
docs: Validate JP2 requirements on colour specification boxes.