docs: private boolean checkImplementer(TypeElement providerImplementer, TypeElement providerType) {
  
      String verify = processingEnv.getOptions().get("verify");
      if (verify == null || !Boolean.valueOf(verify)) {
        return true;
      }
  
      // TODO: We're currently only enforcing the subtype relationship
      // constraint. It would be nice to enforce them all.
  
      Types types = processingEnv.getTypeUtils();
  
      return types.isSubtype(providerImplementer.asType(), providerType.asType());
    }