code: function(record, json, relationship) {
          var attr = relationship.key;
          var type = this.keyForRelationship(relationship.type);
          var key = this.keyForRelationship(attr);
  
          if (relationship.kind === 'hasMany') {
            json.relationships = json.relationships || {};
            json.relationships[key] = hasManyLink(key, type, record, attr);
          }
        }
docs: Use "links" key