code: def set_vibration(self, left_motor, right_motor, duration):
          
          if left_motor and right_motor:
              return self._spin_up(self.double_rumble, duration/1000)
          if left_motor:
              return self._spin_up(self.left_rumble, duration/1000)
          if right_motor:
              return self._spin_up(self.right_rumble, duration/1000)
          return -1
docs: Control the speed of both motors seperately or together.
          left_motor and right_motor arguments require a number:
          0 (off) or 1 (full).
          duration is miliseconds, e.g. 1000 for a second.