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Complete this python program:
def _sliding_window(times, window, sfreq):
assistant
#Here is the Python program you requested.

    """Aux function of GeneralizationAcrossTime.
    Define the slices on which to train each classifier. The user either define
    the time slices manually in window[\slices\] or s/he passes optional params
    to set them from window[\start\], window[\stop\], window[\step\] and
    window[\length\].
    Parameters
    times : ndarray, shape (n_times,)
    Array of times from MNE epochs.
    window : dict keys: (\start\, \stop\, \step\, \length\)
    Either train or test times.
    Returns
    window : dict
    Dictionary to set training and testing times.
    See Also
    GeneralizationAcrossTime
    """
    import copy
    window = _DecodingTime(copy.deepcopy(window))
    time_slices = window.get('slices', None)
    if (time_slices is None):
        window['start'] = window.get('start', times[0])
        window['stop'] = window.get('stop', times[(-1)])
        window['step'] = window.get('step', (1.0 / sfreq))
        window['length'] = window.get('length', (1.0 / sfreq))
        if (not (times[0] <= window['start'] <= times[(-1)])):
            raise ValueError(('start    (%.2f    s)    outside    time    range    [%.2f,    %.2f].' % (window['start'], times[0], times[(-1)])))
        if (not (times[0] <= window['stop'] <= times[(-1)])):
            raise ValueError(('stop    (%.2f    s)    outside    time    range    [%.2f,    %.2f].' % (window['stop'], times[0], times[(-1)])))
        if (window['step'] < (1.0 / sfreq)):
            raise ValueError('step    must    be    >=    1    /    sampling_frequency')
        if (window['length'] < (1.0 / sfreq)):
            raise ValueError('length    must    be    >=    1    /    sampling_frequency')
        if (window['length'] > np.ptp(times)):
            raise ValueError('length    must    be    <=    time    range')
        def find_t_idx(t):
            return np.argmin(np.abs((np.asarray(times) - t)))
        start = find_t_idx(window['start'])
        stop = find_t_idx(window['stop'])
        step = int(round((window['step'] * sfreq)))
        length = int(round((window['length'] * sfreq)))
        time_slices = [range(start, (start + length))]
        while ((time_slices[(-1)][0] + step) <= ((stop - length) + 1)):
            start = (time_slices[(-1)][0] + step)
            time_slices.append(range(start, (start + length)))
        window['slices'] = time_slices
    window['times'] = _set_window_time(window['slices'], times)
    return window