code: def seek(self, idx):
          
          assert not self.writable
          self._check_pid(allow_reset=True)
          pos = ctypes.c_size_t(self.idx[idx])
          check_call(_LIB.MXRecordIOReaderSeek(self.handle, pos))
docs: Sets the current read pointer position.
  
          This function is internally called by `read_idx(idx)` to find the current
          reader pointer position. It doesn't return anything.