How to solve Shape Plugin issue?

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Hello, fellows

I would like to beg your help.

I am trying to apply OSM bright styles to OSM data (downloaded from geofabrik) in TileMill.

But when I transferred the code from original files into my project files with extension: *mss I got error on a a stage of application styles for roads_high, bridges and tunnels.
```
/* ---- Casing ----------------------------------------------- */
#roads_high::outline[zoom>=11][zoom<=20],
#tunnel[render='1_outline'][zoom>=11][zoom<=20],
#bridge[render='1_outline'][zoom>=11][zoom<=20]{
/* -- colors & styles -- */
```
I tried to save but the program gave me an output:
`Shape Plugin: no attribute 'render' in 'C:\path\to\the\project\luxembourg-latest-free.shp\gis.osm_roads_free_1'. Valid attributes are: osm_id,code,fclass,name,ref,oneway,maxspeed,layer,bridge,tunnel.`

What could it be can somebody tell me please? And what is the meaning of 'render' parameter where may I find it?

And I also do not understand what 'stylegroup' stands for?

Thank You

Start by comparing the selectors in the copied .mss files with the attributes listed for the shapefile, especially render, bridge, and tunnel. Review the original OSM Bright files and the Shape Plugin context for the meanings of render and stylegroup. Done means identifying the source of the missing attribute and documenting the required data or style changes.

Written by the indexing model from the issue text.