code: @Beta
    public static <R, C, V> RowSortedTable<R, C, V> unmodifiableRowSortedTable(
        RowSortedTable<R, ? extends C, ? extends V> table) {
      /*
       * It's not ? extends R, because it's technically not covariant in R. Specifically,
       * table.rowMap().comparator() could return a comparator that only works for the ? extends R.
       * Collections.unmodifiableSortedMap makes the same distinction.
       */
      return new UnmodifiableRowSortedMap<>(table);
    }
docs: Returns an unmodifiable view of the specified row-sorted table. This method allows modules to
  provide users with "read-only" access to internal tables. Query operations on the returned
  table "read through" to the specified table, and attempts to modify the returned table, whether
  direct or via its collection views, result in an {@code UnsupportedOperationException}.
  
  <p>The returned table will be serializable if the specified table is serializable.
  
  @param table the row-sorted table for which an unmodifiable view is to be returned
  @return an unmodifiable view of the specified table
  @since 11.0