+ /**
+ * Get the instance of an item from the collection if only ID is specified.
+ *
+ * If more than one argument is supplied, all are expected to be IDs and
+ * the last to be a function callback that will be invoked when the requested
+ * items are available.
+ *
+ * @see {api.Values.when}
+ *
+ * @param {string} id ID of the item.
+ * @param {...} Zero or more IDs of items to wait for and a callback
+ * function to invoke when they're available. Optional.
+ * @return {mixed} The item instance if only one ID was supplied.
+ * A Deferred Promise object if a callback function is supplied.
+ */