code: def _get_index_mapred_emu(self, bucket, index, startkey, endkey=None):
          
          phases = []
          if not self.phaseless_mapred():
              phases.append({'language': 'erlang',
                             'module': 'riak_kv_mapreduce',
                             'function': 'reduce_identity',
                             'keep': True})
          if endkey:
              result = self.mapred({'bucket': bucket,
                                    'index': index,
                                    'start': startkey,
                                    'end': endkey},
                                   phases)
          else:
              result = self.mapred({'bucket': bucket,
                                    'index': index,
                                    'key': startkey},
                                   phases)
          return [key for resultbucket, key in result]
docs: Emulates a secondary index request via MapReduce. Used in the
          case where the transport supports MapReduce but has no native
          secondary index query capability.