@Override
  @SuppressWarnings("unchecked")
  public CalendarAttendeeModel apply(Map<String, Object> attendee, TransformerContext context) {
    if (attendee == null) {
      return null;
    }

    boolean optional = !attendee.getOrDefault("type", "false").equals("required");
    Map<String, ?> emailAddress = (Map<String, ?>) attendee.get("emailAddress");
    String displayName = TransformerHelper.getString("name", emailAddress).orElse("");
    String email = TransformerHelper.getString("address", emailAddress).orElse("");

    return new CalendarAttendeeModel(displayName, email, optional);
  }
Maps from a Graph API calendar attendee resource as defined by
https://developer.microsoft.com/en-us/graph/docs/api-reference/beta/resources/attendee
extensions/data-transfer/portability-data-transfer-microsoft/src/main/java/org/datatransferproject/transfer/microsoft/transformer/calendar/ToCalendarAttendeeModelTransformer.java