'Returns the discretized `ZerosPolesGain` system.
Parameters: See `cont2discrete` for details.
Returns
sys: instance of `dlti` and `ZerosPolesGain`'

def to_discrete(self, dt, method='zoh', alpha=None):

    return ZerosPolesGain(dt=dt, *cont2discrete((self.zeros, self.poles, self.gain), dt, method=method, alpha=alpha)[:(-1)])
