async _isEditable(oOverlay, mPropertyBag) {
			try {
				const [bAsSibling, bAsChild] = await Promise.all([
					this._isEditableCheck(mPropertyBag.sourceElementOverlay, true),
					this._isEditableCheck(mPropertyBag.sourceElementOverlay, false)
				]);
				return {
					asSibling: bAsSibling,
					asChild: bAsChild
				};
			} catch (oError) {
				Log.error(oError);
			}
		}
This function gets called on startup. It checks if the Overlay is editable by this plugin.
@param {sap.ui.dt.Overlay} oOverlay - Overlay to be checked
@param {object} mPropertyBag - Additional data for the check
@returns {object} Returns object with editable boolean values for "asChild" and "asSibling"
@override