code: @Override
    public void close() {
      if (state == RELEASED) {
        return;
      }
      if (state == READY) {
        LIB.mdb_txn_abort(ptr);
      }
      keyVal.close();
      state = RELEASED;
    }
docs: Closes this transaction by aborting if not already committed.
  
  <p>
  Closing the transaction will invoke
  {@link BufferProxy#deallocate(java.lang.Object)} for each read-only buffer
  (ie the key and value).