text: import mongoose from 'mongoose';
  const Schema = mongoose.Schema;
  
  const ArticleSchema = new Schema({
    owner: {type: Schema.Types.ObjectId, required: true, ref: 'User'},
    title: { type: String, required: true },
    content: { type: String, required: true },
    tags: { type: [String] },
    comments: [{type: Schema.Types.ObjectId, required: true, ref: 'Comment'}],
    likes: [{type: Schema.Types.ObjectId, required: true, ref: 'Like'}],
    create_time: { type: Date, required: true, default: Date.now },
    origin: {type: Schema.Types.ObjectId, required: false, ref: 'Article'}
  });
  ArticleSchema.index({ _id: 1 });
  export default mongoose.model('Article', ArticleSchema);