如何使用mongoose删除子文档？

const mongoose = require('mongoose');

const childSchema = new mongoose.Schema({
  name: String,
  age: Number
});

const parentSchema = new mongoose.Schema({
  name: String,
  children: [childSchema]
});

const Parent = mongoose.model('Parent', parentSchema);
const Child = mongoose.model('Child', childSchema);

Parent.findOne({ name: 'John' }, (err, parent) => {
  if (err) {
    console.error(err);
    return;
  }

  // 找到要删除的子文档
  const child = parent.children.id('childId');
});

child.remove();

parent.save((err) => {
  if (err) {
    console.error(err);
    return;
  }

  console.log('子文档删除成功！');
});