text: const mongoose = require('mongoose');
  
  const schema = new mongoose.Schema({
    name: {type: String},
    parent: {type: mongoose.SchemaTypes.ObjectId, ref: 'Category'}
  })
  
  schema.virtual('children', {
    localField: '_id',
    foreignField: 'parent',
    justOne: false,
    ref: 'Category'
  })
  
  module.exports = mongoose.model('Category', schema, 'Categorys')