private ImmutableSet<TypeElement> getSupportedAnnotationTypeElements(Step step) {
    return step.annotations().stream()
        .map(elementUtils::getTypeElement)
        .filter(Objects::nonNull)
        .collect(toImmutableSet());
  }
An optional hook for logic to be executed at the end of each round.
common/src/main/java/com/google/auto/common/BasicAnnotationProcessor.java