[DAR-4788][External] Allow download of frames extracted from videos & multi-slotted items

[JBWilkie]

Problem

• 1: darwin-py will download 2 files for every frame that was extracted from a video upon upload: The frame itself, and the video file. This results in massively duplicated data, much slower downloads (due to re-downloading videos), and an incorrect local folder structure
• 2: darwin-py will crash when trying to pull a release where any file is a multi-slotted item or a DICOM series

Solution

Problem 1 occurs because on upload, each extracted frame is associated with two source files:

• 1: The frame itself
• 2: The video from which the frame was extracted

When darwin-py encounters a slot associated with >1 source file, it tries to download every source file. This PR makes the following change: There are only 2 supported types of data where >1 source file can be associated with a slot, so we check:

• If the slot is a DICOM series, or:
• If the slot is an extracted frame, in which case it will have exactly 2 source files: 1 image and 1 video

If we detect an extracted frame, we select only the image for download. If we find that the slot is neither supported type of data, we raise an error

Problem 2 occurs because we are trying to access each source file with source_file.file_name. source_file is a dictionary, so instead we need to do source_file["file_name"]

Changelog

Resolved issues with:

• Pulling frames extracted from videos
• Pulling multi-slotted items & DICOM series

[linear]

DAR-4788 BUG: Unable to pull release that include files that were pushed as frames