MvnFreeNPathMetric doesn't work as expected in test_all_types.py

[0pdd]

The puzzle 852-b1d29a15 from #852 has to be resolved:

aibolit/test/metrics/npath/test_all_types.py

Lines 547 to 550 in b5d1b0a

	# @todo #852:60min Fix MvnFreeNPathMetric for moderate NPath complexity case
	# It is necessary to fix implementation of MvnFreeNPathMetric
	# so that the test on a moderate NPath complexity case passes.
	# Once fixed, remove `pytest.mark.xfail` decorator.

The puzzle was created by Yegor Bugayenko on 13-Jul-25.

Estimate: 60 minutes, role: DEV.

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