code: function(data) {
          // Data indexing
          this._rtree = rbush(9);
          data = data || [];
          var array = [];
          var that = this;
          function index(d) {
              var bbox = that._getBoundingBox(d);
              if (bbox) {
                  var key = that._toIndexKey(bbox);
                  key.data = d;
                  array.push(key);
              }
          }
          if (typeof data === 'function') {
              data = data();
          }
          if (typeof data.forEach === 'function') {
              data.forEach(index);
          } else if (data.length) {
              for (var i = 0; i < data.length; i++) {
                  index(data[i]);
              }
          }
          this._rtree.load(array);
      }
docs: Indexes the specified data array using a RTree index.