There is one behavior of [labelbinarizer](http://scikit-learn.org/stable/modules/generated/sklearn.preprocessing.LabelBinarizer.html) 

```
import numpy as np
from sklearn import preprocessing
lb = preprocessing.LabelBinarizer()
lb.fit(np.array([[0, 1, 1], [1, 0, 0]]))
lb.classes_

```

The output is `array([0, 1, 2])`. Why there is a 2 there?