Easier loggers traversal tree with a logger.getChildren method

[sblondon]

BPO	45095
Nosy	@sblondon

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-09-03.17:01:49.814>
labels = ['type-feature', 'library', '3.11']
title = 'Easier loggers traversal tree with a logger.getChildren method'
updated_at = <Date 2021-09-03.17:01:49.814>
user = 'https://github.com/sblondon'

bugs.python.org fields:

activity = <Date 2021-09-03.17:01:49.814>
actor = 'sblondon'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-09-03.17:01:49.814>
creator = 'sblondon'
dependencies = []
files = []
hgrepos = []
issue_num = 45095
keywords = []
message_count = 1.0
messages = ['401006']
nosy_count = 1.0
nosy_names = ['sblondon']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue45095'
versions = ['Python 3.11']

[sblondon]

Currently, logging.root.manager.loggerDict is usable to do a homemade traversal of the loggers tree. However, it's not a public interface. Adding a 'logger.getChildren()' method would help to implement the traversal. The method would return a set of loggers.

Usage example:
>>> import logging
>>> logging.basicConfig(level=logging.CRITICAL)
>>> root_logger = logging.getLogger()
<RootLogger root (CRITICAL)>
>>> root_logger.getChildren()
set()
>>> a_logger = logging.getLogger("a")
>>> root_logger.getChildren()
{<Logger a. (CRITICAL)>}
>>> logging.getLogger('a.b').setLevel(logging.DEBUG)
>>> _ = logging.getLogger('a.c')
>>> a_logger.getChildren()
{<Logger a.c (CRITICAL)>, <Logger a.b (DEBUG)>}

With such method, traverse the tree will be obvious to write with a recursive function.

Use cases:

• to check all the loggers are setted up correctly. I wrote a small function to get all loggers, and log on every level to check the real behaviour.
• to draw the loggers tree like logging_tree library (https://pypi.org/project/logging_tree/). I didn't ask to logging_tree's maintainer but I don't think he would use such function because the library works for huge range of python releases.

I plan to write a PR if someone thinks it's a good idea.