new_contents: # This code is licensed under the MIT License (see LICENSE file for details)
  
  from ris_widget import ris_widget; rw = ris_widget.RisWidget()
  import pathlib
  rw.add_image_files_to_flipbook(pathlib.Path('/Users/zpincus/Documents/Research/Pincus Lab/Data/raw_image_demo/').glob('*.png'))
  from ris_widget import split_view
  split_view.split_view_rw(rw)
  from ris_widget.overlay import free_spline
  fs = free_spline.FreeSpline(rw)
  from ris_widget.qwidgets import annotator
  spline_field = annotator.OverlayAnnotation('centerline', fs)
  rw.add_annotator(fields=[spline_field])
  # load tcks into tck_list
  annotations = [{'centerline':tck} for tck in tck_list]
  rw.annotator.all_annotations = annotations
subject: add spline annotation example