code: public void seal() {
      lockedParameterNamesSet = ImmutableSet.copyOf(lockedParameterNamesSet);
      lockedParameterNamesScopeMap = ImmutableMap.copyOf(Maps.transformValues(lockedParameterNamesScopeMap, new Function<Set<String>, Set<String>>() {
        @Override
        public Set<String> apply(Set<String> input) {
          return ImmutableSet.copyOf(input);
        }
      }));
      sealed = true;
    }
docs: Make all maps and sets immutable.