Quick fixes for type map conversion issues related to empty lists

[karlhigley]

These are the quick fixes I made in order to get list features working, as described in this comment on #1640. I'm submitting this PR in order to share the code more than to get it merged, since I know there's a larger effort to improve testing of the type map beyond these fixes.

[feast-ci-bot]

@karlhigley: Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

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[codecov-commenter]

Codecov Report

Merging #1846 (0758dcc) into master (0dc13f0) will decrease coverage by 20.71%.
The diff coverage is 36.36%.

@@             Coverage Diff             @@
##           master    #1846       +/-   ##
===========================================
- Coverage   84.45%   63.73%   -20.72%     
===========================================
  Files          90       90               
  Lines        6773     6776        +3     
===========================================
- Hits         5720     4319     -1401     
- Misses       1053     2457     +1404     

Flag	Coverage Δ
integrationtests	?
unittests	63.73% <36.36%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
sdk/python/feast/type_map.py	50.00% <36.36%> (-32.86%)	⬇️
.../integration/online_store/test_online_retrieval.py	17.39% <0.00%> (-82.61%)	⬇️
.../integration/online_store/test_universal_online.py	18.03% <0.00%> (-81.97%)	⬇️
sdk/python/tests/utils/online_read_write_test.py	18.18% <0.00%> (-81.82%)	⬇️
...fline_store/test_universal_historical_retrieval.py	20.00% <0.00%> (-80.00%)	⬇️
...gration/registration/test_feature_service_apply.py	31.25% <0.00%> (-68.75%)	⬇️
sdk/python/feast/infra/online_stores/datastore.py	30.32% <0.00%> (-63.12%)	⬇️
sdk/python/feast/infra/online_stores/redis.py	30.35% <0.00%> (-62.50%)	⬇️
sdk/python/tests/data/data_creator.py	38.09% <0.00%> (-61.91%)	⬇️
sdk/python/feast/infra/online_stores/dynamodb.py	30.37% <0.00%> (-60.76%)	⬇️
... and 41 more

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[adchia]

Hey! So we ended up adding a test suite for types in https://github.com/feast-dev/feast/blob/master/sdk/python/tests/integration/registration/test_universal_types.py

Notably, if we add an empty list test case, there's still quite a few failures I think. Would you mind adding a test and fixing the other parts that go wrong?

[adchia]

Sorry actually seems like it works fine as is. Just tested it with https://gist.github.com/adchia/b242be8d066e15a7f26852400b1d2c59 and saw that this fix indeed fixes the empty list test case when you add it!

[achals]

/lgtm

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: achals, karlhigley

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[feast-ci-bot]

New changes are detected. LGTM label has been removed.

[judahrand]

I'm going through the loop of adding tests for this in the PR which I originally opened #1703. Shall we keep discussion there?

[karlhigley]

@judahrand Yeah, sounds good to me. Once your PR covers this case, we can close this one.