code: public PassengerSegmentInfoBuilder addPassengerSegmentInfo(
  			String segmentId, String passengerId, String seat, String seatType) {
  		return new PassengerSegmentInfoBuilder(this, segmentId, passengerId,
  				seat, seatType);
  	}
docs: Adds a {@link PassengerSegmentInfo} object to this template. This field
  is mandatory for this template. There must be at least one element.
  
  @param segmentId
  used to identify a flight segment. It can't be empty and must
  be unique within the itinerary.
  @param passengerId
  the passengerId of {@link PassengerInfo} object. It can't be
  empty and it must match an actual passenger.
  @param seat
  the seat number for the passenger. It can't be empty.
  @param seatType
  the seat type for the passenger (e.g. Economy comfort). It
  can't be empty.
  @return the passenger segment info builder