Determines which join parameters are unique

def get_unique_ajps( benchmark_runs ):
        """
        Determines which join parameters are unique
        """
        br_ajps = {}
        for br in benchmark_runs:
            for ajp in br.additional_join_parameters:
                if ajp not in br_ajps:
                    br_ajps[ajp] = set()
                br_ajps[ajp].add( br.additional_join_parameters[ajp]['short_name'] )
        unique_ajps = []
        for ajp in br_ajps:
            if len( br_ajps[ajp] ) > 1:
                unique_ajps.append( ajp )
        return unique_ajps