of int
        Number of non-zero values in the array along a given axis.
        Otherwise, the total number of non-zero values in the array
        is returned.

    See Also
    --------
    nonzero : Return the coordinates of all the non-zero values.

    Examples
    --------
    >>> np.count_nonzero(np.eye(4))
    4
    >>> a = np.array([[0, 1, 7, 0],
    ...               [3, 0, 2, 19]])
    >>> np.count_nonzero(a)
    5
    >>> np.count_nonzero(a, axis=0)
    array([1, 1, 2, 1])
    >>> np.count_nonzero(a, axis=1)
    array([2, 3])
    >>> np.count_nonzero(a, axis=1, keepdims=True)
    array([[2],
           [3]])
    NF)