@Override
  public CalendarModel apply(Map<String, Object> calendar, TransformerContext context) {
    String id = (String) calendar.get("id");
    if (id == null) {
      context.problem("Calendar id not found");
      return null;
    }

    String name = (String) calendar.get("name");
    if (name == null) {
      context.problem("Calendar name not found");
      return null;
    }
    return new CalendarModel(
        id, name, name); // use name as description since it does not exist in Office
  }
Maps from a Graph API calendar resource as defined by:
https://developer.microsoft.com/en-us/graph/docs/api-reference/beta/resources/calendar.
extensions/data-transfer/portability-data-transfer-microsoft/src/main/java/org/datatransferproject/transfer/microsoft/transformer/calendar/ToCalendarModelTransformer.java