ValueError: not enough values to unpack (expected 3, got 2)

[metavinayak]

Traceback (most recent call last):
File "crop_boxes.py", line 87, in
box_extraction("sample_image.jpg", "./Cropped/") #image to be extracted, directory where to save cropped images
File "crop_boxes.py", line 72, in box_extraction
_, contours, hierarchy = cv2.findContours(img_final_bin, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
ValueError: not enough values to unpack (expected 3, got 2)
'''