docs: def start_asweep(self, start=None, stop=None, step=None):
          """Starts a amplitude sweep.
  
          :param start: Sets the start frequency.
          :param stop: Sets the target frequency.
          :param step: Sets the frequency step.
  
          """
          if start:
              self.amplitude_start = start
          if stop:
              self.amplitude_stop = stop
          if step:
              self.amplitude_step = step
          self._write(('SWEEP', Integer), 2)