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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 tag(self, value):
 """The name of the program that generated the log message. The tag can only contain alphanumeric characters. If the tag is longer than {MAX_TAG_LEN} characters it will be truncated automatically. """

        if value is None:
            value = sys.argv[0]
        self._tag = value[:self.MAX_TAG_LEN]