l below which to zero elements.
        `k` == 0 is the main diagonal, `k` < 0 subdiagonal and
        `k` > 0 superdiagonal.

    Returns
    -------
    triu : ndarray
        Return matrix with zeroed elements below the kth diagonal and has
        same shape and type as `m`.

    Examples
    --------
    >>> from scipy.linalg import triu
    >>> triu([[1,2,3],[4,5,6],[7,8,9],[10,11,12]], -1)
    array([[ 1,  2,  3],
           [ 4,  5,  6],
           [ 0,  8,  9],
           [ 0,  0, 12]])

    r-