code: def step_amp(self):
          
          difference = self.drift_target - self._raw_value
          if abs(difference) < self.change_rate:
              self.value = self.drift_target
          else:
              delta = self.change_rate * numpy.sign(difference)
              self.value = self._raw_value + delta
docs: Change the amplitude according to the change rate and drift target.
  
          Returns: None