Reactivty and prepareDerivedData

import { propertyStore } from '#runtime/svelte/store/writable-derived';

class MyActor extends Actor 
{
   // For typing consider creating a class that contains the derived data.
   #derived = { value1: 0 };

   /** @type {ActorStores} */
   @stores;

   constructor()
   {
      this.#stores = {
         value1: propertyStore(this, 'value1'),
      };
   }

   /** 
    * Returns derived data stores.
    * @returns {ActorStores} Derived data stores.
    */
   get stores() { return this.#stores; }

   /** 
    * @returns {number} Value 1
    */
   get value1() { return this.#derived.value1; }
   
   /** 
    * @param {number} newValue New value 1.
    */
   set value1(newValue) { this.#stores.value1.set(newValue); }
}

/**
 * @typedef ActorStores
 * 
 * @property {import('svelte/store').Writable<number>} Value 1
 */

import { propertyStore } from '#runtime/svelte/store/writable-derived';

class MyActor extends Actor 
{
   // For typing consider creating a class that contains the derived data.
   #derived = { value1: 0 };

   /** @type {ActorStores} */
   @stores;

   constructor()
   {
      this.#stores = {
         value1: propertyStore(this, 'value1'),
      };
   }

   /** 
    * Returns derived data stores.
    * @returns {ActorStores} Derived data stores.
    */
   get stores() { return this.#stores; }

   /** 
    * @returns {number} Value 1
    */
   get value1() { return this.#derived.value1; }
   
   /** 
    * @param {number} newValue New value 1.
    */
   set value1(newValue) { this.#stores.value1.set(newValue); }
}

/**
 * @typedef ActorStores
 * 
 * @property {import('svelte/store').Writable<number>} Value 1
 */

<script>
  import { getContext } from 'svelte';

  // 'actor' is a TJSDocument.
  const actor = getContext('actor');

  // Value 1 is a store.
  let value1 = $actor.stores.value1;
</script>

Value 1: {$value1}

<script>
  import { getContext } from 'svelte';

  // 'actor' is a TJSDocument.
  const actor = getContext('actor');

  // Value 1 is a store.
  let value1 = $actor.stores.value1;
</script>

Value 1: {$value1}

<script>
  import { getContext } from 'svelte';

  // 'actor' is a TJSDocument.
  const actor = getContext('actor');
</script>

Value 1: {$actor.value1}

<script>
  import { getContext } from 'svelte';

  // 'actor' is a TJSDocument.
  const actor = getContext('actor');
</script>

Value 1: {$actor.value1}

console.log(this.#stores.bonus)
this.#stores.bonus.set(this.getBonus());

console.log(this.#stores.bonus)
this.#stores.bonus.set(this.getBonus());

TypeError: Failed data preparation for Actor.2qJ5YYtsYFtaJRVz.Item.q9dDkAZpdeKhTkPi. store.subscribe is not a function
    at subscribe (utils.js:139:22)
    at index.js:158:4
    at Array.map (<anonymous>)
    at index.js:157:38
    at Object.subscribe2 [as subscribe] (index.js:82:11)
    at update (index.js:68:34)
    at Object.set (index.js:91:16)
    at set bonus [as bonus] (item.js?t=1698093657038:32:22)
    at LeobrewItem._prepareDerivedBonuses (item.js?t=1698093657038:52:15)
    at LeobrewItem.prepareDerivedData (item.js?t=1698093657038:46:8)

TypeError: Failed data preparation for Actor.2qJ5YYtsYFtaJRVz.Item.q9dDkAZpdeKhTkPi. store.subscribe is not a function
    at subscribe (utils.js:139:22)
    at index.js:158:4
    at Array.map (<anonymous>)
    at index.js:157:38
    at Object.subscribe2 [as subscribe] (index.js:82:11)
    at update (index.js:68:34)
    at Object.set (index.js:91:16)
    at set bonus [as bonus] (item.js?t=1698093657038:32:22)
    at LeobrewItem._prepareDerivedBonuses (item.js?t=1698093657038:52:15)
    at LeobrewItem.prepareDerivedData (item.js?t=1698093657038:46:8)

    constructor(...args) {
        super(...args);

                const derivedWritable = writable(this.#derived);
        this.#stores = {
            bonus: propertyStore(derivedWritable, "bonus"),
            subSkills: propertyStore(derivedWritable, "subSkills"),
        };
    }

    constructor(...args) {
        super(...args);

                const derivedWritable = writable(this.#derived);
        this.#stores = {
            bonus: propertyStore(derivedWritable, "bonus"),
            subSkills: propertyStore(derivedWritable, "subSkills"),
        };
    }