+ /**
+ * Change the source of the given {@link Story} (the source is the main
+ * information used to group the stories together).
+ * <p>
+ * In other words, <b>move</b> the {@link Story} into other source.
+ * <p>
+ * The source can be a new one, it needs not exist before hand.
+ *
+ * @param luid
+ * the luid of the {@link Story} to move
+ * @param newSource
+ * the new source
+ */
+ void changeSource(String luid, String newSource) {