如何才能仅获得以Angular 6 rxjs表示的最后一个可观察输出？

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs';

@Component({
  selector: 'app-example',
  template: `
    <button (click)="getData()">获取数据</button>
  `,
})
export class ExampleComponent implements OnInit {
  data$: Observable<any>;

  ngOnInit() {
    this.data$ = this.getDataFromServer();
  }

  getDataFromServer(): Observable<any> {
    // 模拟从服务器获取数据的异步操作
    return new Observable<any>((observer) => {
      setTimeout(() => {
        observer.next('数据1');
      }, 1000);

      setTimeout(() => {
        observer.next('数据2');
      }, 2000);

      setTimeout(() => {
        observer.next('数据3');
        observer.complete(); // 完成可观察序列
      }, 3000);
    });
  }

  getData() {
    this.data$.pipe(
      last()
    ).subscribe((lastData) => {
      console.log('最后一个可观察输出:', lastData);
    });
  }
}