docs: private String generatedBuilderSimpleName(TypeElement type) {
      String packageName = elements.getPackageOf(type).getQualifiedName().toString();
      String originalName = type.getQualifiedName().toString();
      checkState(originalName.startsWith(packageName + "."));
      String nameWithoutPackage = originalName.substring(packageName.length() + 1);
      return String.format(BUILDER_SIMPLE_NAME_TEMPLATE, nameWithoutPackage.replaceAll("\\.", "_"));
    }