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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 add_argument_group(self, title, description=None):
 """Add an argument group, or return a pre-existing one."""

        try:
            groups = self.__groups
        except AttributeError:
            groups = self.__groups = {}

        if title not in groups:
            groups[title] = super().add_argument_group(
                title=title, description=description)

        return groups[title]