How to use the impedance.models.circuits.fitting.circuit_fit function in impedance

#    impedance: array of complex numbers
        #    impedance and frequency match in length

        assert isinstance(frequencies, np.ndarray),\
            'frequencies is not of type np.ndarray'
        assert isinstance(frequencies[0], (float, int, np.int32, np.float64)),\
            'frequencies does not contain a number'
        assert isinstance(impedance, np.ndarray),\
            'impedance is not of type np.ndarray'
        assert isinstance(impedance[0], (complex, np.complex128)),\
            'impedance does not contain complex numbers'
        assert len(frequencies) == len(impedance),\
            'mismatch in length of input frequencies and impedances'

        if self.initial_guess is not None:
            parameters, conf = circuit_fit(frequencies, impedance,
                                           self.circuit, self.initial_guess,
                                           self.constants, method=method,
                                           bounds=bounds)
            self.parameters_ = parameters
            if conf is not None:
                self.conf_ = conf
        else:
            # TODO auto calc guess
            raise ValueError('no initial guess supplied')

        return self

#    impedance: array of complex numbers
        #    impedance and frequency match in length

        assert isinstance(frequencies, np.ndarray),\
            'frequencies is not of type np.ndarray'
        assert isinstance(frequencies[0], (float, int, np.int32, np.float64)),\
            'frequencies does not contain a number'
        assert isinstance(impedance, np.ndarray),\
            'impedance is not of type np.ndarray'
        assert isinstance(impedance[0], (complex, np.complex128)),\
            'impedance does not contain complex numbers'
        assert len(frequencies) == len(impedance),\
            'mismatch in length of input frequencies and impedances'

        if self.initial_guess is not None:
            parameters, conf = circuit_fit(frequencies, impedance,
                                           self.circuit, self.initial_guess,
                                           self.constants, method=method,
                                           bounds=bounds)
            self.parameters_ = parameters
            if conf is not None:
                self.conf_ = conf
        else:
            # TODO auto calc guess
            raise ValueError('no initial guess supplied')

        return self