How to use CARTO cdb_route_with_waypoints function

query.sql

WITH ap AS (
  SELECT 
    array_agg(the_geom) as arr
  FROM 
    etapas
  )
SELECT 
  (cdb_route_with_waypoints(arr, 'walk')).*
FROM 
  ap

style.css

/* Camino */

#layer_line{
line-color: #3EBCAE;
line-width: 1.5;
line-opacity: 1;
}

/* Lugares */

Map {
  buffer-size: 2000;
    }
#layer{
  marker-fill-opacity: 1;
  marker-line-color: #B40903;
  marker-line-width: 1;
  marker-line-opacity: 0;
  marker-placement: point;
  marker-type: ellipse;
  marker-width: 3;
  marker-fill: #F11810;
  marker-allow-overlap: true;
    }
#layer::point{
  marker-fill-opacity: 0.5;
  marker-line-color: #B40903;
  marker-line-width: 1;
  marker-line-opacity: 1;
  marker-placement: point;
  marker-type: ellipse;
  marker-width: 20;
  marker-fill: #F11810;
  marker-allow-overlap: true;
}
#layer::labels {
  text-name: [lugar];
  text-face-name: "Open Sans Bold";
  text-size: 12;
  text-fill: #FFFFFF;
  text-halo-fill: fadeout(#000000, 30%);
  text-halo-radius: 2;
  text-allow-overlap: true;
  text-placement: point;
  text-placement-type: simple;
  text-dy: 10;
}