docs: def _delete_vdev_info(self, vdev):
          """handle vdev related info."""
          vdev = vdev.lower()
          network_config_file_name = self._get_network_file()
          device = self._get_device_name(vdev)
          cmd = '\n'.join(("num=$(sed -n '/auto %s/=' %s)" % (device,
                                                      network_config_file_name),
                          "dns=$(awk 'NR==(\"\'$num\'\"+6)&&"
                          "/dns-nameservers/' %s)" %
                                                      network_config_file_name,
                          "if [[ -n $dns ]]; then",
                          "  sed -i '/auto %s/,+6d' %s" % (device,
                                                      network_config_file_name),
                          "else",
                          "  sed -i '/auto %s/,+5d' %s" % (device,
                                                      network_config_file_name),
                          "fi"))
          return cmd