code: function linestringGeoJSON(geometry, opts) {
      var feature = {
          type:'Feature',
          geometry: geometry
      }
      geometry = buffer(feature, 0.00001, 'miles').features[0].geometry;
      var rings = geometry.coordinates;
  
      var cover_options = {
          min: opts.index_min_level,
          max: opts.index_max_level,
          max_cells: opts.max_index_cells,
          type: 'polygon'
      };
  
      var llRings = rings.map(function(ring) {
          return ring.map(function(c) {
              var latLng = (new s2.S2LatLng(c[1], c[0])).normalized();
              return latLng.toPoint();
          }).slice(1);
      });
      var features = s2.getCover(llRings, cover_options).map(function(cell,i) {
          var geojson = cell.toGeoJSON();
          return {
              type: 'Feature',
              geometry: geojson,
              properties: {}
          };
      });
  
      return {
          type: 'FeatureCollection',
          features: features
      }
  }
docs: GeometryGeoJSON