code: def recover_devices(cls):
          
  
          if "_devices" in globals():
              return
  
          global _devices
          confs_dir = os.path.abspath(os.path.normpath(cfg.CONF.dhcp_confs))
          for netid in os.listdir(confs_dir):
              conf_dir = os.path.join(confs_dir, netid)
              intf_filename = os.path.join(conf_dir, 'interface')
              try:
                  with open(intf_filename, 'r') as f:
                      ifname = f.read()
                  _devices[netid] = ifname
              except IOError:
                  LOG.error('Unable to read interface file: %s',
                            intf_filename)
              LOG.debug("Recovered device %s for network %s'",
                        ifname, netid)
docs: Track devices.
  
          Creates global dict to track device names across driver invocations
          and populates based on current devices configured on the system.