title: ValueError: not enough values to unpack (expected 3, got 2). What went wrong?
body: <p>I got this code from online. Can someone help me what went wrong?
  Here's the snippet where the error popped up:</p>
  <pre class="lang-py prettyprint-override"><code>import cv2
  import numpy as np
  
  _, contours, _ = cv2.findContours(Nucleus_img, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
  pad_del = np.zeros_like(Nucleus_img)
  </code></pre>