docs: public void putMultiple(final T key, final T val, final int elements,
                            final PutFlags... op) {
      if (SHOULD_CHECK) {
        requireNonNull(txn);
        requireNonNull(key);
        requireNonNull(val);
        txn.checkReady();
        txn.checkWritesAllowed();
      }
      final int mask = mask(op);
      if (SHOULD_CHECK && !isSet(mask, MDB_MULTIPLE)) {
        throw new IllegalArgumentException("Must set " + MDB_MULTIPLE + " flag");
      }
      txn.kv().keyIn(key);
      final Pointer dataPtr = txn.kv().valInMulti(val, elements);
      final int rc = LIB.mdb_cursor_put(ptrCursor, txn.kv().pointerKey(),
                                        dataPtr, mask);
      checkRc(rc);
    }