Changes to GetFieldValues in output module

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.83333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 85.17%. Comparing base (33460bf) to head (cd3ea13). Report is 1 commits behind head on main.

Files	Patch %	Lines
plaso/output/rawpy.py	92.59%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #4853 +/- ## ========================================== - Coverage 85.18% 85.17% -0.01% ========================================== Files 427 427 Lines 38563 38561 -2 ========================================== - Hits 32849 32844 -5 - Misses 5714 5717 +3 ```

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