Syncing of Calendar with iCloud lose the CalendarI

Question

I am developing a Calendar App. In which calendars can be create by user and also need the iCloud Syncing feature so that user can get the same calendars on his/her other device. Now according to Apple Document:

A full sync with the calendar will lose this identifier. You should have a plan for dealing with a calendar whose identifier is no longer fetchable by caching its other properties.

CalendarIdentifier property of EKCalendar is not reliable. And using other properties we can not differentiate the calendar as well that it is made by iOS Native Calendar App or My Calendar App. So I am stuck here and trying to find any reliable solution. But not able to find till now so please help me for this to get the solution. I will be thankful to you.