 changes within the template to these properties
       *   will result in `notifyInstanceProp` being called.
       * - `mutableData`: When `true`, the generated class will skip strict
       *   dirty-checking for objects and arrays (always consider them to be
       *   "dirty").
       * - `notifyInstanceProp(instance, property, value)`: Called when
       *   an instance property changes.  Users may choose to call `notifyPath`
       *   on e.g. the owner to notify the change.
       * - `parentModel`: