IVS-878 - Increase Test Coverage & Performance

[rw-bsi]

Changes:

• increase test coverage + fix for IMPLEMENTATION_LEVEL

Test output:

============================= test session starts ==============================
platform darwin -- Python 3.11.0, pytest-8.3.4, pluggy-1.5.0
rootdir: /Users/user/Projects/bsi/step-file-parser
plugins: anyio-4.13.0
collected 77 items
test_parser.py ....................s.............ss...s................. [ 74%]
.................... [100%]
======================== 73 passed, 4 skipped in 4.40s =========================
Finished running tests!