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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 change_score_for(self, member, delta, member_data=None):
        '''
        Change the score for a member in the leaderboard by a score delta which can be positive or negative.

        @param member [String] Member name.
        @param delta [float] Score change.
        @param member_data [String] Optional member data.
        '''
        self.change_score_for_member_in(self.leaderboard_name, member, delta, member_data)