+ /**
+ * @private
+ * Sets the values of one or more of the items within the CheckboxGroup
+ * @param {String|Array|Object} id Can take multiple forms. Can be optionally:
+ * <ul>
+ * <li>An ID string to be used with a second argument</li>
+ * <li>An array of the form ['some', 'list', 'of', 'ids', 'to', 'mark', 'checked']</li>
+ * <li>An array in the form [true, true, false, true, false] etc, where each item relates to the check status of
+ * the checkbox at the same index</li>
+ * <li>An object containing ids of the checkboxes as keys and check values as properties</li>
+ * </ul>
+ * @param {String} value The value to set the field to if the first argument was a string
+ */