Add networks submodule. #543

Job	Run time
code-coverage	3m 26s
run_tests_notebooks (ubuntu-latest, 3.9)	5m 6s
run_tests (ubuntu-latest, 3.9)	3m 11s
run_tests_notebooks (ubuntu-latest, 3.10)	5m 18s
run_tests (ubuntu-latest, 3.10)	2m 58s
run_tests_notebooks (ubuntu-latest, 3.11)	5m 27s
run_tests (ubuntu-latest, 3.11)	4m 27s
run_tests_notebooks (macos-latest, 3.9)	10m 48s
run_tests (macos-latest, 3.9)	9m 47s
run_tests_notebooks (macos-latest, 3.10)	14m 34s
run_tests (macos-latest, 3.10)	2m 52s
run_tests_notebooks (macos-latest, 3.11)	13m 28s
run_tests (macos-latest, 3.11)	8m 33s
	1h 29m 55s

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