code: def occupied_by_sort(self, address):
          idx = self._search(address)
          if len(self._list) <= idx:
              return None
          if self._list[idx].start <= address < self._list[idx].end:
              return self._list[idx].sort
          if idx > 0 and address < self._list[idx - 1].end:
              return self._list[idx - 1].sort
          return None