code: def add_check(self, check):
          
          if check is None:
              return
          if check.uuid in self.checks:
              logger.debug("Already existing check: %s", check)
              return
          logger.debug("Adding a check: %s", check)
  
          # Add a new check to the scheduler checks list
          self.checks[check.uuid] = check
          self.nb_checks += 1
  
          # Raise a brok to inform about a next check is to come ...
          # but only for items that are actively checked
          item = self.find_item_by_id(check.ref)
          if item.active_checks_enabled:
              self.add(item.get_next_schedule_brok())
docs: Add a check into the scheduler checks list
  
          :param check: check to add
          :type check: alignak.check.Check
          :return: None