feat(ops): add `tree_iter` function #804

Job	Run time
Test for Python 3.10 on ubuntu-latest	3m 3s
Test for Python 3.10 on windows-latest	3m 42s
Test for Python 3.10 on macos-latest	2m 35s
Test for Python 3.7 on ubuntu-latest	56s
Test for Python 3.8 on ubuntu-latest	58s
Test for Python 3.9 on ubuntu-latest	1m 4s
Test for Python 3.11 on ubuntu-latest	56s
Test for Python 3.12 on ubuntu-latest	1m 3s
Test for Python 3.7 on windows-latest	2m 1s
Test for Python 3.8 on windows-latest	2m 2s
Test for Python 3.9 on windows-latest	2m 28s
Test for Python 3.11 on windows-latest	1m 52s
Test for Python 3.12 on windows-latest	2m 6s
Test for Python 3.7 on macos-latest	1m 39s
Test for Python 3.8 on macos-latest	1m 11s
Test for Python 3.9 on macos-latest	1m 58s
Test for Python 3.11 on macos-latest	1m 22s
Test for Python 3.12 on macos-latest	1m 13s
	32m 9s

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