 If the `classes` parameter is set, `y` will not be
    iterated.

Returns
-------
y_indicator : {ndarray, sparse matrix} of shape (n_samples, n_classes)
    A matrix such that `y_indicator[i, j] = 1` iff `classes_[j]`
    is in `y[i]`, and 0 otherwise. Sparse matrix will be of CSR
    format.
NŠ