Replace the datetime in obj.value with an ISO 8601 string.

def transformFromNative(cls, obj):
        """Replace the datetime in obj.value with an ISO 8601 string."""
        # print('transforming from native')
        if obj.isNative:
            obj.isNative = False
            tzid = TimezoneComponent.registerTzinfo(obj.value.tzinfo)
            obj.value = dateTimeToString(obj.value, cls.forceUTC)
            if not cls.forceUTC and tzid is not None:
                obj.tzid_param = tzid
            if obj.params.get('X-VOBJ-ORIGINAL-TZID'):
                if not hasattr(obj, 'tzid_param'):
                    obj.tzid_param = obj.x_vobj_original_tzid_param
                del obj.params['X-VOBJ-ORIGINAL-TZID']

        return obj