docs: def _useChunk(self, index) -> None:
          """
          Switch to specific chunk
  
          :param index:
          """
  
          if self.currentChunk is not None:
              if self.currentChunkIndex == index and \
                      not self.currentChunk.closed:
                  return
              self.currentChunk.close()
  
          self.currentChunk = self._openChunk(index)
          self.currentChunkIndex = index
          self.itemNum = self.currentChunk.numKeys + 1