def METHOD_NAME(self, channel, att_mu, rf_switch=True):
    """
    Sets attenuators on chosen shift register (channel).
    :param channel: index of the register [0-3]
    :param att_mu: attenuation setting in machine units [0-63]
    :param rf_switch: rf switch (bool)
    """
    self.channel_sw[channel] = 1 if rf_switch else 0
    self.att_mu[channel] = att_mu
    self._update_register(channel)