docs: private ImmutableMap<String, Optional<? extends Element>> deferredElements() {
      ImmutableMap.Builder<String, Optional<? extends Element>> deferredElements =
          ImmutableMap.builder();
      for (ElementName elementName : deferredElementNames) {
        deferredElements.put(elementName.name(), elementName.getElement(elements));
      }
      return deferredElements.build();
    }