BUG: handle predicted annotations with no segments, fix #393

[NickleDave]

See rationale for this fix on that issue:
https://github.com/NickleDave/vak/issues/393
and related bug report in
https://github.com/NickleDave/vak/issues/386

• change lbl_tb2segments to return all Nones
  when lbl_tb passed in is all 'unlabeled' class
• also add logic to lbl_tb2segment to handle case
  where post-processing removes all labeled segments;
  in that case again return all Nones
• change vak.core.predict so it just continues
  when lbl_tb2segments returns all Nones
  • i.e. do not create an Annotation instance for the vocalization

[NickleDave]

@avanikop after making these fixes I was able to run vak predict using your config + checkpoint + data without a crash

I will also add tests for this.
Would you be okay @avanikop with me adding your checkpoint and a couple of the data files (specifically the ones that end up being "not labeled") to this public dataset?
https://osf.io/vz48c/
I will not share all the files, just the one or two I need to replicate the cases where it predicts no segments

It would be great @avanikop @marichard123 if you could check this branch out and test that it works for you, and also behaves as you expect.

To do that, you'd need to

• set up a development install with a local copy of this repo
• check out the branch

For a dev install, you'll want to follow instructions here:
https://vak.readthedocs.io/en/latest/get_started/installation.html#installation-from-source-e-g-for-development
@avanikop I think the steps for setting up an environment should work as-is for you on Mac but I haven't tested.
@marichard123 you might run into issues with torch not playing well with poetry. If so, please let me know and we can figure out a workaround.
Once you get the code copied and cloned into an environment, you'll want to check out the branch.
You can do that with git wherever you clone the code:

(vak-env) ~/code/vak $ git checkout -t origin/add-logic-handle-predicted-no-annotations-#393

Let me know and I can help if you get stuck on any of that.
Any feedback you can give me will be much appreciated!

[NickleDave]

Unit tests passed for me locally so this doesn't seem to have broken anything else.
Will wait to see what the CI says.

[NickleDave]

I am going to go ahead and merge this and release a new dev version, so ppl can test by installing that

[NickleDave]

@all-contributors please add @Luke-Poeppel for doc

@Luke-Poeppel I'll be sure to credit you for other contributions when I merge them (like a contributing.md!) -- working on it!

[allcontributors]

@NickleDave

I've put up a pull request to add @Luke-Poeppel! 🎉

[NickleDave]

whoops @Luke-Poeppel I meant to comment on your PR
🤔 It still seemed to work though, shows your commits when I click on the book emoji in the README