title: Clone an image in cv2 python
body: <p>I'm new to opencv, here is a question, what is the python function which act the same as cv::clone() in cpp?
  I just try to get a rect by </p>
  
  <pre><code>    rectImg = img[10:20, 10:20]
  </code></pre>
  
  <p>but when I draw a line on it ,I find the line appear both on img and the rectImage,so , how can I get this done?</p>