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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_family(self, major_number):
 """ Expand to a new release line with given ``major_number``. This will flesh out mandatory buckets like ``unreleased_bugfix`` and do other necessary bookkeeping. """

        # Normally, we have separate buckets for bugfixes vs features
        keys = ['unreleased_bugfix', 'unreleased_feature']
        # But unstable prehistorical releases roll all up into just
        # 'unreleased'
        if major_number == 0 and self.config.releases_unstable_prehistory:
            keys = ['unreleased']
        # Either way, the buckets default to an empty list
        self[major_number] = {key: [] for key in keys}