code: def fetch_check(self, master):
          '''check for missing parameters periodically'''
          if self.param_period.trigger():
              if master is None:
                  return
              if len(self.mav_param_set) == 0:
                  master.param_fetch_all()
              elif self.mav_param_count != 0 and len(self.mav_param_set) != self.mav_param_count:
                  if master.time_since('PARAM_VALUE') >= 1:
                      diff = set(range(self.mav_param_count)).difference(self.mav_param_set)
                      count = 0
                      while len(diff) > 0 and count < 10:
                          idx = diff.pop()
                          master.param_fetch_one(idx)
                          count += f fetch_check(self, master):
          '''check for missing parameters periodically'''
          if self.param_period.trigger():
              if master is None:
                  return
              if len(self.mav_param_set) == 0:
                  master.param_fetch_all()
              elif self.mav_param_count != 0 and len(self.mav_param_set) != self.mav_param_count:
                  if master.time_since('PARAM_VALUE') >= 1:
                      diff = set(range(self.mav_param_count)).difference(self.mav_param_set)
                      count = 0
                      while len(diff) > 0 and count < 10:
                          idx = diff.pop()
                          master.param_fetch_one(idx)
                          count += 1
docs: check for missing parameters periodically