code: public void delete(final PutFlags... f) {
      if (SHOULD_CHECK) {
        checkNotClosed();
        txn.checkReady();
        txn.checkWritesAllowed();
      }
      final int flags = mask(f);
      checkRc(LIB.mdb_cursor_del(ptrCursor, flags));
    }
docs: Delete current key/data pair.
  
  <p>
  This function deletes the key/data pair to which the cursor refers.
  
  @param f flags (either null or {@link PutFlags#MDB_NODUPDATA}