Write all events to the calendar

def write_items(self, calendar):
        """
        Write all events to the calendar
        """
        for item in self.items:
            event = Event()
            for ifield, efield in ITEM_EVENT_FIELD_MAP:
                val = item.get(ifield)
                if val is not None:
                    event.add(efield, val)
            calendar.add_component(event)