async load(mPropertyBag) {
			mPropertyBag.reference = ManifestUtils.getFlexReferenceForSelector(mPropertyBag.selector);

			if (
				!mPropertyBag.reference
				|| !mPropertyBag.containerKey
			) {
				throw new Error("not all mandatory properties were provided for the loading of the personalization");
			}

			await FlexState.initialize({
				componentId: mPropertyBag.selector.getId()
			});
			return UI2PersonalizationState.getPersonalization(mPropertyBag.reference, mPropertyBag.containerKey, mPropertyBag.itemName);
		}
Retrieves a personalization object stored for an application under a given container ID and item name;
in case no itemName is given all items for the given container key are returned.

@param {object} mPropertyBag - Object with parameters as properties
@param {sap.ui.fl.Selector} mPropertyBag.selector - Used to retrieve the associated flex persistence
@param {string} mPropertyBag.containerKey The key of the container in which the personalization was stored
@param {string} [mPropertyBag.itemName] The item name under which the personalization was stored
@returns {Promise} Promise resolving with the object stored under the passed container key and item name,
or undefined in case no entry was stored for these;
in case no sItemName was passed all entries known for the container key

@private
@ui5-restricted