
    Step response of discrete-time system.

    Parameters
    ----------
    system : tuple of array_like
        A tuple describing the system.
        The following gives the number of elements in the tuple and
        the interpretation:

            * 1: (instance of `dlti`)
            * 3: (num, den, dt)
            * 4: (zeros, poles, gain, dt)
            * 5: (A, B, C, D, dt)

    x0 : array_like, optional
        Initial state-vector.  Defaults to zero.
    t : array_like, optional
        Time points.  Computed if not given.
    n : int, optional
        The number of time points to compute (if `t` is not given).

    Returns
    -------
    tout : ndarray
        Output time points, as a 1-D array.
    yout : ndarray
        Step response of system.  Each element of the tuple represents
        the output of the system based on a step response to each input.

    See Also
    --------
    step, dimpulse, dlsim, cont2discrete

    