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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 rank_member_across(
            self, leaderboards, member, score, member_data=None):
        '''
        Rank a member across multiple leaderboards.

        @param leaderboards [Array] Leaderboard names.
        @param member [String] Member name.
        @param score [float] Member score.
        @param member_data [String] Optional member data.
        '''
        for leaderboard_name in leaderboards:
            self.rank_member_in(leaderboard, member, score, member_data)