'Handle object conversion if input is an instance of `lti`'

def __new__(cls, *system, **kwargs):

    if ((len(system) == 1) and isinstance(system[0], LinearTimeInvariant)):
        return system[0].to_zpk()
    if (cls is ZerosPolesGain):
        if (kwargs.get('dt') is None):
            return ZerosPolesGainContinuous.__new__(ZerosPolesGainContinuous, *system, **kwargs)
        else:
            return ZerosPolesGainDiscrete.__new__(ZerosPolesGainDiscrete, *system, **kwargs)
    return super(ZerosPolesGain, cls).__new__(cls)
