code: def update_position(self, newpos):
          '''update trail'''
          tnow = time.time()
          if tnow >= self.last_time + self.timestep:
              self.points.append(newpos.latlon)
              self.last_time = tnow
              while len(self.points) > self.count:
                  self.points.pop(0f update_position(self, newpos):
          '''update trail'''
          tnow = time.time()
          if tnow >= self.last_time + self.timestep:
              self.points.append(newpos.latlon)
              self.last_time = tnow
              while len(self.points) > self.count:
                  self.points.pop(0)
docs: update trail