If a given logger is not assigned a level, then
it inherits one from its closest ancestor
with an assigned level.
The root logger resides at the top
of the logger hierarchy. It always exists and
always has an assigned level.
Level Inheritance Rule
The inherited level for a given logger
C, is equal to the first non-null level in the
logger hierarchy, starting at C and proceeding
upwards in the hierarchy towards the root
logger.
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