Fix deepcopy logic for new Python

[fjarri]

itertools.count() is not copyable anymore.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
alysis/_node.py	0.00%	6 Missing ⚠️

Files with missing lines	Coverage Δ
alysis/_node.py	36.89% <0.00%> (-1.28%)	⬇️

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