Disparity map on opencv 2.4

Hy! I am using openCv 2.4 with python 2.7. I wanted to make a disparity map from 2 stereo images and after a googling i found a good example in: https://github.com/Itseez/opencv/blob/master/samples/python2/stereo_match.py But i don't get all the attributes of StereoSGBM even if i have read the documentation: http://docs.opencv.org/modules/calib3d/doc/camera_calibration_and_3d_reconstruction.html#stereosgbm Does anyone explain me better the code?? thanks