docs: public T get(final Txn<T> txn, final T key) {
      if (SHOULD_CHECK) {
        requireNonNull(txn);
        requireNonNull(key);
        txn.checkReady();
      }
      txn.kv().keyIn(key);
      final int rc = LIB.mdb_get(txn.pointer(), ptr, txn.kv().pointerKey(), txn
                                 .kv().pointerVal());
      if (rc == MDB_NOTFOUND) {
        return null;
      }
      checkRc(rc);
      return txn.kv().valOut(); // marked as out in LMDB C docs
    }