title: What is the idea behind an empty model?
body: <p>I have to classify images using python and cv2. Before training the model, we have to first create an empty model using</p>
  <pre><code>cv2.ml.KNearest_create()
  </code></pre>
  <p>I understand that this line of code creates an empty model, but what does that mean? When I think of a model, I generally imagine an equation like y = mx + b or y = ax^2 + bx + c. I'm curious as to what an empty model object looks like and how it can be used to fit training data.</p>