How to use `cv2.findContours` in different OpenCV versions?

An alternative to work with 2.x 、3.x、4.x is:

cnts, hiers = cv2.findContours(...)[-2:]

Notice:

cv2.findContours

OpenCV 3.x

OpenCV 4.0

In OpenCV 3.4:

findContours(image, mode, method[, contours[, hierarchy[, offset]]]) -> image, contours, hierarchy

In OpenCV 4.0:

findContours(image, mode, method[, contours[, hierarchy[, offset]]]) -> contours, hierarchy