private TypeMirror getContainedPrimitiveType(Types typeUtils) {
    String simpleName = optionalType.asElement().getSimpleName().toString();
    TypeKind typeKind = PRIMITIVE_TYPE_KINDS.get(simpleName);
    Verify.verifyNotNull(typeKind, "Could not get contained type of %s", optionalType);
    return typeUtils.getPrimitiveType(typeKind);
  }
Returns a string representing the method call to obtain the empty version of this Optional.
This will be something like {@code "Optional.empty()"} or possibly {@code
"java.util.Optional.empty()"}. It does not have a final semicolon.

<p>This method is public so that it can be referenced as {@code p.optional.empty} from
templates.
value/src/main/java/com/google/auto/value/processor/Optionalish.java