Add unit tests for lccr_csv reader

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (35a2cec) 69.49% compared to head (5584cb9) 71.35%.

Files	Patch %	Lines
tests/test_lccr_csv_reader.py	97.95%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #168 +/- ## ========================================== + Coverage 69.49% 71.35% +1.86% ========================================== Files 35 36 +1 Lines 2255 2304 +49 ========================================== + Hits 1567 1644 +77 + Misses 688 660 -28 ```

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