def METHOD_NAME(self, freq_list, return_freq=False):
    """
    Run frequency list sweep using sequential trigger.
    :param freq_list: list of frequencies
    :param return_freq: if True, returns the frequencies read from the instrument
    Returns values as configured with :attr:`~.AgilentE4980.mode`
        """
    # manual, page 299
    # self.write("*RST;*CLS")
    self.write("TRIG:SOUR BUS")
    self.write("DISP:PAGE LIST")
    self.write("FORM ASC")
    # trigger in sequential mode
    self.write("LIST:MODE SEQ")
    lista_str = ",".join(['%e' % f for f in freq_list])
    self.write("LIST:FREQ %s" % lista_str)
    # trigger
    self.write("INIT:CONT ON")
    self.write(":TRIG:IMM")
    # wait for completed measurement
    # using the Error signal (there should be a better way)
    while 1:
        try:
            measured = self.values(":FETCh:IMPedance:FORMatted?")
            break
        except VisaIOError:
            pass
    # at the end return to manual trigger
    self.write(":TRIG:SOUR HOLD")
    # gets 4-ples of numbers, first two are data A and B
    a_data = [measured[_] for _ in range(0, 4 * len(freq_list), 4)]
    b_data = [measured[_] for _ in range(1, 4 * len(freq_list), 4)]
    if return_freq:
        read_freqs = self.values("LIST:FREQ?")
        return a_data, b_data, read_freqs
    else:
        return a_data, b_data