docs: def _series_sis(self):
          """Return image series in Olympus SIS file."""
          pages = self.pages._getlist(validate=False)
          page = pages[0]
          lenpages = len(pages)
          md = self.sis_metadata
          if 'shape' in md and 'axes' in md:
              shape = md['shape'] + page.shape
              axes = md['axes'] + page.axes
          elif lenpages == 1:
              shape = page.shape
              axes = page.axes
          else:
              shape = (lenpages,) + page.shape
              axes = 'I' + page.axes
          self.is_uniform = True
          return [TiffPageSeries(pages, shape, page.dtype, axes, kind='SIS')]