@Override
        public NotificationCompat.Builder extend(NotificationCompat.Builder builder) {

            Bundle carExtensions = new Bundle();

            if (mLargeIcon != null) {
                carExtensions.putParcelable(EXTRA_LARGE_ICON, mLargeIcon);
            }
            if (mColor != NotificationCompat.COLOR_DEFAULT) {
                carExtensions.putInt(EXTRA_COLOR, mColor);
            }

            if (mUnreadConversation != null) {
                Bundle b = getBundleForUnreadConversation(mUnreadConversation);
                carExtensions.putBundle(EXTRA_CONVERSATION, b);
            }

            builder.getExtras().putBundle(EXTRA_CAR_EXTENDER, carExtensions);
            return builder;
        }
Apply car extensions to a notification that is being built. This is typically called by
the {@link NotificationCompat.Builder#extend(NotificationCompat.Extender)}
method of {@link NotificationCompat.Builder}.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/compat/NotificationCompat.java