Hmm. The newer versions of Rhythm should have had the doc input, (2019.6.1 is pretty out of date).
However, I did not like the option of having a doc input, so I just updated the node for it to find what document the sheet came from.
Note: Working with linked files this way is pretty darn unstable. So run manually, and be patient. lol
Get this version and give it a try,
