Entity.java

/**
     * Default implementation of {@link #getRef()} method based on type and id.
     * <p>
     * This method create ref which looks like this: "type_name:id"
     * This is most often used in API as ref, but there is no guaranty.
     */
    @NonNull
    static String createRef(@EntityType int entityType,
                     @Nullable String entityId) {
        return EntityType.Utils.getApiName(entityType) + ":" + entityId;
    }