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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def start(self, level="WARN"):
 """ Start logging with this logger. Until the logger is started, no messages will be emitted. This applies to all loggers with the same name and any child loggers. Messages less than the given priority level will be ignored. The default level is 'WARN', which conforms to the *nix convention that a successful run should produce no diagnostic output. Available levels and their suggested meanings: DEBUG - output useful for developers INFO - trace normal program flow, especially external interactions WARN - an abnormal condition was detected that might need attention ERROR - an error was detected but execution continued CRITICAL - an error was detected and execution was halted """

        if self.active:
            return
        handler = StreamHandler()  # stderr
        handler.setFormatter(Formatter(self.LOGFMT))
        self.addHandler(handler)
        self.setLevel(level.upper())
        self.active = True
        return