anchor.diff:          type = types.lines;
           default = ''stdin { type => "example" }'';
           description = "Logstash input configuration.";
  -        example = ''
  +        example = literalExample ''
             # Read from journal
             pipe {
               command => "''${pkgs.systemd}/bin/journalctl -f -o json"
  
positive.code: 
        outputConfig = mkOption {
          type = types.lines;
          default = ''stdout { debug => true debug_format => "json"}'';
          description = "Logstash output configuration.";
          example = ''
            redis { host => "localhost" data_type => "list" key => "logstash" codec => json }
  
negative.code:         type = types.lines;
          default = ''noop {}'';
          description = "logstash filter configuration.";
          example = literalExample ''
            if [type] == "syslog" {
              # Keep only relevant systemd fields
              # http://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html
  