mongoose virtuals with typescript error -包含箭头函数捕获'this‘的全局值，该值隐式具有类型'any’

import { Schema, model, Document } from 'mongoose';

interface IUser extends Document {
  firstName: string;
  lastName: string;
}

const userSchema = new Schema<IUser>({
  firstName: String,
  lastName: String
});

// 使用函数表达式定义虚拟属性的getter和setter
userSchema.virtual('fullName').get(function(this: IUser) {
  return `${this.firstName} ${this.lastName}`;
}).set(function(this: IUser, fullName: string) {
  const [firstName, lastName] = fullName.split(' ');
  this.firstName = firstName;
  this.lastName = lastName;
});

const User = model<IUser>('User', userSchema);

// 创建用户实例
const user = new User({
  firstName: 'John',
  lastName: 'Doe'
});

console.log(user.fullName); // 输出: John Doe