如何使用nestjs/mongoose在schema类中定义mongoose方法？

npm install --save @nestjs/mongoose mongoose

import { Module } from '@nestjs/common';
import { MongooseModule } from '@nestjs/mongoose';
import { CatsController } from './cats.controller';
import { CatsService } from './cats.service';
import { CatSchema } from './schemas/cat.schema';

@Module({
  imports: [
    MongooseModule.forRoot('mongodb://localhost/nestjs'),
    MongooseModule.forFeature([{ name: 'Cat', schema: CatSchema }]),
  ],
  controllers: [CatsController],
  providers: [CatsService],
})
export class CatsModule {}

import * as mongoose from 'mongoose';

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

CatSchema.methods.meow = function() {
  console.log('Meow!');
};

import { Injectable } from '@nestjs/common';
import { InjectModel } from '@nestjs/mongoose';
import { Model } from 'mongoose';
import { Cat } from './interfaces/cat.interface';

@Injectable()
export class CatsService {
  constructor(@InjectModel('Cat') private catModel: Model<Cat>) {}

  async create(cat: Cat): Promise<Cat> {
    const createdCat = new this.catModel(cat);
    return createdCat.save();
  }

  async findAll(): Promise<Cat[]> {
    return this.catModel.find().exec();
  }
}

import { Controller, Get, Post, Body } from '@nestjs/common';
import { CatsService } from './cats.service';
import { Cat } from './interfaces/cat.interface';

@Controller('cats')
export class CatsController {
  constructor(private readonly catsService: CatsService) {}

  @Post()
  async create(@Body() createCatDto: Cat): Promise<Cat> {
    return this.catsService.create(createCatDto);
  }

  @Get()
  async findAll(): Promise<Cat[]> {
    return this.catsService.findAll();
  }
}