Get command keys for subcommands

[dvora-h]

Pull Request check-list

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Description of change

fixes #2165

[codecov-commenter]

Codecov Report

Merging #2170 (bda5864) into master (5c99e27) will decrease coverage by 0.08%.
The diff coverage is 10.34%.

@@ Coverage Diff @@ ## master #2170 +/- ## ========================================== - Coverage 91.98% 91.89% -0.09%  ========================================== Files 105 105 Lines 25287 25313 +26 ========================================== + Hits 23260 23262 +2  - Misses 2027 2051 +24 

Impacted Files	Coverage Δ
redis/cluster.py	91.72% <ø> (ø)
tests/test_cluster.py	97.54% <ø> (+0.05%)	⬆️
redis/commands/parser.py	68.13% <4.34%> (-20.28%)	⬇️
redis/client.py	88.76% <25.00%> (-0.28%)	⬇️
tests/test_commands.py	90.04% <50.00%> (+<0.01%)	⬆️
redis/asyncio/client.py	91.98% <0.00%> (-0.18%)	⬇️

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