PYTHON-5781 Coverage increase for `network_layer.py` #10146

Job	Run time
Python 3.10-ubuntu-latest	13m 6s
Coverage	13m 59s
Typing Tests (3.10)	1m 7s
Python pypy-3.11-ubuntu-latest	14m 8s
Test minimum dependencies and Python	54s
Typing Tests (3.11)	1m 5s
static	2m 47s
Python 3.15-ubuntu-latest	12m 50s
Python 3.13t-ubuntu-latest	13m 0s
Integration Tests	55s
Docs Checks	44s
DocTest	1m 0s
Make an sdist	19s
Install from SDist and Test	1m 10s
	1h 17m 4s

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