code: public List<Excerpt> getValueTypeAnnotations() {
      if (valueTypeAnnotations instanceof ImmutableList) {
        valueTypeAnnotations = new ArrayList<>(valueTypeAnnotations);
      }
      return Collections.unmodifiableList(valueTypeAnnotations);
    }
docs: Returns an unmodifiable view of the list that will be returned by {@link
  Datatype#getValueTypeAnnotations()}. Changes to this builder will be reflected in the view.