This is that I want:
Make a render with this layer (barrancabermeja/mapa_tematico_malla_GBD), I added that layer but it includes the sublayers ( ancho calzada (0), tipo de capa de rodadura (1), numero de carriles (2) ).
When I print the operational layers (and other thematic layers too) I see the structure of the layer above, but It doesnt have the fields property. I think that I need the fields to make the renderer. But, I dont know How to get the fields of each sublayer there.
If I add one layer like mapserver/0 (barrancabermeja/mapa_tematico_malla_GBD/0) , and I print that in the console, I can see the fields property, otherwise, not.