code: public static CalibrationDetectorChessboard2 chessboard2(@Nullable ConfigChessboard2 config , ConfigGridDimen dimen ) {
  		if( config == null )
  			config = new ConfigChessboard2();
  		config.checkValidity();
  
  		return new CalibrationDetectorChessboard2(config,dimen);
  	}
docs: Detector for chessboard targets.  Squares can be partially outside, but inside corners must be entirely
  inside the image.
  
  @see DetectChessboardFiducial
  
  @param config Configuration for chessboard detector
  @return Square grid target detector.