code: @Override
      protected void _from(ObjectInput in) throws IOException,
              ClassNotFoundException {
          // 1: read number of table namespaces
          final int size = in.readInt();
          for (int i = 0; i < size; i++) {
              final TableNamespace ns = new TableNamespace();
              // 1: read table namespace
              ns.readExternal(in);
              // 2: read number of documents
              final int documentsSize = in.readInt();
              for (int j = 0; j < documentsSize; j++) {
                  // 1: read document index
                  addNamespace(ns, in.readInt());
              }
          }
      }
docs: {@inheritDoc}