title: how do i combine multiple category feature into X_train_cat_tr
body: <pre><code>lb_encoder_1 = LabelBinarizer()
  X_train_cat_tr_1 = lb_encoder_1.fit_transform(X_train_cat_1)
  
  lb_encoder_2 = LabelBinarizer()
  X_train_cat_tr_2 = lb_encoder_2.fit_transform(X_train_cat_2)
  
  lb_encoder_3 = LabelBinarizer()
  X_train_cat_tr_3 = lb_encoder_3.fit_transform(X_train_cat_3)
  </code></pre>
  <p>When I combined them using np.hstack, it comes out with the error that all the input array dimensions for the concatenation axis must match exactly, but along dimension 0, the array at index 0 has size 39681 and the array at index 1 has size 39922. How should i combine them into X_train_cat_tr?</p>