class Interaction { HistoryNode? historyNode; int? graphVersion; Interaction({ this.historyNode, this.graphVersion, }); factory Interaction.fromJson(Map json) => Interaction( historyNode: json["history_node"] == null ? null : HistoryNode.fromJson(json["history_node"]), graphVersion: json["graph_version"], ); } class HistoryNode { int? nodeId; String? title; int? cid; HistoryNode({ this.nodeId, this.title, this.cid, }); factory HistoryNode.fromJson(Map json) => HistoryNode( nodeId: json["node_id"], title: json["title"], cid: json["cid"], ); }