code: def warning(self):
          
          signals, docs, overs = self.expandedStim()
          if np.any(np.array(overs) > 0):
              msg = 'Stimuli in this test are over the maximum allowable \
                  voltage output. They will be rescaled with a maximum \
                  undesired attenuation of {:.2f}dB.'.format(np.amax(overs))
              return msg
          return 0
docs: Checks Stimulus for any warning conditions
  
          :returns: str -- warning message, if any, 0 otherwise