如何在TypeORM中存根嵌套存储库？

@Entity()
export class ParentEntity {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @OneToMany(type => ChildEntity, child => child.parent, { cascade: true })
  children: ChildEntity[];
}

@Entity()
export class ChildEntity {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @ManyToOne(type => ParentEntity, parent => parent.children)
  parent: ParentEntity;
}

@EntityRepository(ParentEntity)
export class ParentRepository extends Repository<ParentEntity> {
  async saveWithChildren(parent: ParentEntity): Promise<ParentEntity> {
    const childRepository = getRepository(ChildEntity);
    parent.children = await Promise.all(parent.children.map(child => childRepository.save(child)));
    return this.save(parent);
  }
}

@EntityRepository(ChildEntity)
export class ChildRepository extends Repository<ChildEntity> {}

import { createConnection } from "typeorm";
import { ParentEntity, ChildEntity } from "./entities";
import { ParentRepository, ChildRepository } from "./repositories";

createConnection({
  type: "mysql",
  host: "localhost",
  port: 3306,
  username: "root",
  password: "password",
  database: "database",
  entities: [ParentEntity, ChildEntity],
  synchronize: true,
  logging: true,
  subscribers: [],
  migrations: [],
  cli: {
    entitiesDir: "src/entities",
    migrationsDir: "src/migrations",
    subscribersDir: "src/subscribers"
  }
}).then(connection => {
  connection.getCustomRepository(ParentRepository);
  connection.getCustomRepository(ChildRepository);
});

import { getCustomRepository } from "typeorm";
import { ParentRepository, ChildRepository } from "./repositories";

const parentRepository = getCustomRepository(ParentRepository);
const childRepository = getCustomRepository(ChildRepository);

const parent = new ParentEntity();
parent.name = "Parent";
parent.children = [];

const child1 = new ChildEntity();
child1.name = "Child 1";
child1.parent = parent;

const child2 = new ChildEntity();
child2.name = "Child 2";
child2.parent = parent;

parent.children.push(child1, child2);

parentRepository.saveWithChildren(parent);