docs: @NotNull
      static MetaTreeImpl.Proto saveMetaTree(@NotNull final ITreeMutable metaTree,
                                             @NotNull final EnvironmentImpl env,
                                             @NotNull final ExpiredLoggableCollection expired) {
          final long newMetaTreeAddress = metaTree.save();
          final Log log = env.getLog();
          final int lastStructureId = env.getLastStructureId();
          final long dbRootAddress = log.write(DatabaseRoot.DATABASE_ROOT_TYPE, Loggable.NO_STRUCTURE_ID,
              DatabaseRoot.asByteIterable(newMetaTreeAddress, lastStructureId));
          expired.add(dbRootAddress, (int) (log.getWrittenHighAddress() - dbRootAddress));
          return new MetaTreeImpl.Proto(newMetaTreeAddress, dbRootAddress);
      }