public static <T> Optional<T> ofNullable(T value) {
        return value == null ? empty() : of(value);
    }
Returns an {@code Optional} describing the specified value, if non-null,
otherwise returns an empty {@code Optional}.

@param <T>   the class of the value
@param value the possibly-null value to describe
@return an {@code Optional} with a present value if the specified value
is non-null, otherwise an empty {@code Optional}
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/util/Optional.java