anchor.diff:        ec2_sd_configs = mkOption {
           type = types.listOf promTypes.ec2_sd_config;
           default = [];
  -        apply = x: map _filter x;
           description = ''
             List of EC2 service discovery configurations.
           '';
  
positive.code:       relabel_configs = mkOption {
          type = types.listOf promTypes.relabel_config;
          default = [];
          apply = x: map _filter x;
          description = ''
            List of relabel configurations.
          '';
  
negative.code:   ] ++
    optional (cfg2.webExternalUrl != null) "--web.external-url=${cfg2.webExternalUrl}";
  
    filterValidPrometheus = filterAttrsListRecursive (n: v: !(n == "_module" || v == null || v == [] || v == {}));
    filterAttrsListRecursive = pred: x:
      if isAttrs x then
        listToAttrs (
  