How to use the impedance.fitting.buildCircuit function in impedance

# check that inputs are valid:
        #    frequencies: array of numbers

        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'

        if self._is_fit() and not use_initial:
            return eval(buildCircuit(self.circuit, frequencies,
                                     *self.parameters_,
                                     constants=self.constants, eval_string='',
                                     index=0)[0])
        else:
            print("Simulating circuit based on initial parameters")
            return eval(buildCircuit(self.circuit, frequencies,
                                     *self.initial_guess,
                                     constants=self.constants, eval_string='',
                                     index=0)[0])