如何在rxjs6中结合使用combineLatest和flatMap？

import { combineLatest, Observable } from 'rxjs';
import { flatMap } from 'rxjs/operators';

// 创建多个Observable
const observable1 = new Observable<number>(observer => {
  observer.next(1);
  setTimeout(() => observer.next(2), 1000);
});

const observable2 = new Observable<number>(observer => {
  observer.next(3);
  setTimeout(() => observer.next(4), 2000);
});

// 结合使用combineLatest和flatMap
combineLatest(observable1, observable2)
  .pipe(
    flatMap(([value1, value2]) => {
      // 在这里可以对value1和value2进行处理
      const result = value1 + value2;
      return new Observable<number>(observer => {
        observer.next(result);
        observer.complete();
      });
    })
  )
  .subscribe(result => {
    // 处理转换后的Observable的值
    console.log(result);
  });