Fit label encoder

        Parameters
        ----------
        y : array-like of shape (n_samples,)
            Target values.

        Returns
        -------
        self : returns an instance of self.

def fit(self, X):
        """Fit label encoder

        Parameters
        ----------
        y : array-like of shape (n_samples,)
            Target values.

        Returns
        -------
        self : returns an instance of self.
        """
        X = column_or_1d(X, warn=True)
        _check_numpy_unicode_bug(X)
        self.classes_ = np.unique(X)
        return self