Source code of "flann.knnMatch" and "cv2.SIFT_create()"

I am searching for the source code “flann.knnMatch” and “cv2.SIFT_create()” of these in python, but only function definitions are written. Can any body point me out to the source code of these, it will be great help.
Thanks in advance.

opencv is actually a c++ library, there is no python src code for this
however, have a look here and here

@berak thanks for quick response