code: @Override
    public void close() {
      if (closed) {
        return;
      }
      if (SHOULD_CHECK && !txn.isReadOnly()) {
        txn.checkReady();
      }
      LIB.mdb_cursor_close(ptrCursor);
      kv.close();
      closed = true;
    }
docs: Close a cursor handle.
  
  <p>
  The cursor handle will be freed and must not be used again after this call.
  Its transaction must still be live if it is a write-transaction.