title: What is clf and legend in 'plot_decision_regions'?
body: <pre><code>from mlxtend.plotting import plot_decision_regions
  
  def knn_comparision(data, k):
      X = data[['x1','x2']].values
      y = data['y'].astype(int).values
      clf = neighbors.KNeighborsClassifier(n_neighbors=k)
      clf.fit(X, y)
  
      # Plotting decision regions
      plot_decision_regions(X, y, clf=clf, legend=2)
  </code></pre>
  
  <p>What are the parameters '<strong>clf</strong>' and '<strong>legend</strong>' in plot_decision_regions?</p>