Where do I find "EMD" method?

edit savecancel

I'm using cv2 in python3.5, and all I need is to calculate EMD distance between two n*n matrix. But I have search the whole cv2:

for i in dir(cv2):
if re.match(r'.*emd|EMD.*',i):
    print(i)

And get nothing. So, the problem is, where could I find it? I have read the document and there is an c code implementation.