При попытке выполнения...
Traceback (most recent call last):
File "D:\my_programm_python\feature_detection\feature_detection.py", line 6, in <module>
sift = cv2.xfeatures2d.SIFT_create()
cv2.error: OpenCV(3.4.8) C:\projects\opencv-python\opencv_contrib\modules\xfeatures2d\src\sift.cpp:1207: error: (-213:The function/feature is not implemented) This algorithm is patented and is excluded in this configuration; Set OPENCV_ENABLE_NONFREE CMake option and rebuild the library in function 'cv::xfeatures2d::SIFT::create'