How to use the @nestjs/graphql/dist/utils/extend.util.extend function in @nestjs/graphql

}

    const {
      path,
      disableHealthCheck,
      onHealthCheck,
      cors,
      bodyParserConfig,
      typePaths,
    } = this.options;
    const app = httpAdapter.getInstance();

    // @ts-ignore
    const typeDefs = await this.graphqlTypesLoader.getTypesFromPaths(typePaths);

    const mergedTypeDefs = extend(typeDefs, this.options.typeDefs);
    const apolloOptions = await this.graphqlDistributedFactory.mergeOptions({
      ...this.options,
      typeDefs: mergedTypeDefs,
    });

    if (this.options.definitions && this.options.definitions.path) {
      await this.graphqlFactory.generateDefinitions(
        // @ts-ignore
        printSchema(apolloOptions.schema),
        this.options,
      );
    }

    this.apolloServer = new ApolloServer(apolloOptions as any);
    this.apolloServer.applyMiddleware({
      app,

    return resolvers.reduce((prev, curr) => extend(prev, curr), {});
  }