code: def verify(self, **kwargs):
          
          if 'duration' in kwargs:
              if kwargs['duration'] < self._duration:
                  return "Window size must equal or exceed stimulus length"
          if self._risefall > self._duration:
              return "Rise and fall times exceed component duration"
          return 0
docs: Checks this component for invalidating conditions
  
          :returns: str -- message if error, 0 otherwise