code: def manage_internal_checks(self):
          
          if os.getenv('ALIGNAK_MANAGE_INTERNAL', '1') != '1':
              return
          now = time.time()
          for chk in list(self.checks.values()):
              if not chk.internal:
                  # Exclude checks that are not internal ones
                  continue
  
              # Exclude checks that are not yet ready to launch
              if not chk.is_launchable(now) or chk.status not in [ACT_STATUS_SCHEDULED]:
                  continue
  
              item = self.find_item_by_id(chk.ref)
              # Only if active checks are enabled
              if not item or not item.active_checks_enabled:
                  # Ask to remove the check
                  chk.status = ACT_STATUS_ZOMBIE
                  continue
              logger.debug("Run internal check for %s", item)
  
              self.nb_internal_checks += 1
  
              # Execute internal check
              item.manage_internal_check(self.hosts, self.services, chk, self.hostgroups,
                                         self.servicegroups, self.macromodulations,
                                         self.timeperiods)
              # Ask to consume the check result
              chk.status = ACT_STATUS_WAIT_CONSUME
docs: Run internal checks
  
          :return: None