code: def slice(self, start=0, end=0):
          
          tmp = Gauged.map_new()
          if tmp is None:
              raise MemoryError
          if not Gauged.map_concat(tmp, self.ptr, start, end, 0):
              Gauged.map_free(tmp)  # pragma: no cover
              raise MemoryError
          return SparseMap(tmp)
docs: Slice the map from [start, end)