Logging - How does it work?

A.py

import logging

LOG = logging.getLogger('A')
ch = logging.StreamHandler()
formatter = logging.Formatter('%(asctime)s %(levelname)s %(name)s: %(message)s')
ch.setFormatter(formatter)
LOG.addHandler(ch)
LOG.setLevel("DEBUG")

from functions import common_functions

common_functions.loggertest()

B.py

import logging

LOG = logging.getLogger('B')
ch = logging.StreamHandler()
formatter = logging.Formatter('%(levelname)s %(name)s: %(message)s %(asctime)s')
ch.setFormatter(formatter)
LOG.addHandler(ch)
LOG.setLevel("WARN")

from functions import common_functions

common_functions.loggertest()

functions_common_functions.py

import logging

LOG = logging.getLogger('whichnamehere')
LOG.addHandler(logging.NullHandler())


def loggertest():
    LOG.info("This should be printed with proper formatting.")
    LOG.debug("This debug message as well.")
    LOG.warn("This should be the only message visible for B.py")