original_videos should be a link

[bendichter]

original_videos should be a list of links to ImageSeries objects

[CodyCBakerPhD]

An alternative approach to get use of this in the IBL pipeline faster and cause less immediate trouble for DLC and SLEAP would be a smoother deprecation cycle such as

1. Introduce a new field image_series that does whatever schema magic must be done to specify it as a 'list' of links to ImageSeries
2. Add deprecation warning to original_videos telling people to use the new field instead
3. Once DLC and SLEAP update their usage we can safely remove it

Also for context, this to allow uploading of the videos to DANDI, which only supports external files if they are contained in an ImageSeries - the flip side of adjusting DANDI to be compatible with this field of a PoseEstimation would be much more challenging and too hyper-specific of a treatment just for an extension data type IMO