Gets the stimulus model for calibration

        :param mode: Type of stimulus to get: tone or noise
        :type mode: str
        :returns: :class:`StimulusModel<sparkle.stim.stimulus_model.StimulusModel>`

def calibration_stimulus(self, mode):
        """Gets the stimulus model for calibration

        :param mode: Type of stimulus to get: tone or noise
        :type mode: str
        :returns: :class:`StimulusModel<sparkle.stim.stimulus_model.StimulusModel>`
        """
        if mode == 'tone':
            return self.tone_calibrator.stimulus
        elif mode =='noise':
            return self.bs_calibrator.stimulus