title: OpenCV TypeError: Expected cv::UMat for argument 'src' - What is this?
body: <p>Disclaimer: huge openCV noob</p>
  
  <blockquote>
    <p>Traceback (most recent call last):</p>
    
    <p>File "lanes2.py", line 22, in </p>
  
  <pre><code>canny = canny(lane_image)
  </code></pre>
    
    <p>File "lanes2.py", line 5, in canny</p>
  
  <pre><code>gray = cv2.cvtColor(imgUMat, cv2.COLOR_RGB2GRAY)
  </code></pre>
    
    <p>TypeError: Expected cv::UMat for argument 'src'</p>
  </blockquote>
  
  <p>What exactly is 'src' referring to?</p>