loadModifierResources(modifier) {
    const modifierIndex = modifier.getIndex();
    const modifierLoadId = this.getModifierLoadId(modifier);
    let modifierLoadData = this._modifierLoadDataByLoadId[modifierLoadId];

    // load modifier resources
    if (modifierLoadData == null) {
      // add modifier index to list of applied modifiers
      this._modifierIndices.push(modifierIndex);
      this._modifiers = SDK.GameSession.getInstance().getModifiersByIndices(this._modifierIndices);

      // start new load for modifier resources
      const modifierType = modifier.getType();
      modifierLoadData = this._modifierLoadDataByLoadId[modifierLoadId] = {
        valid: true,
        id: modifierLoadId,
        modifierIndex,
        promise: this.addResourceRequest(modifierLoadId, modifierType),
      };
    }

    return modifierLoadData.promise;
  }
Loads a modifier's resources and returns a promise
@param {SDK.Modifier} modifier
@returns {Promise}