code: def set(self, w, idx):
          '''set a waypoint'''
          w.seq = idx
          if w.seq == self.count():
              return self.add(w)
          if self.count() <= idx:
              raise MAVWPError('adding waypoint at idx=%u past end of list (count=%u)' % (idx, self.count()))
          self.wpoints[idx] = w
          self.last_change = time.time(f set(self, w, idx):
          '''set a waypoint'''
          w.seq = idx
          if w.seq == self.count():
              return self.add(w)
          if self.count() <= idx:
              raise MAVWPError('adding waypoint at idx=%u past end of list (count=%u)' % (idx, self.count()))
          self.wpoints[idx] = w
          self.last_change = time.time()
docs: set a waypoint