TS Error: flatMap, flat, flatten do not exist for type any[] in Angular

Hi everyone! I'm new to TypeScript and Angular, and I've encountered a strange problem. I have a service that receives data from an API. The data comes as an array of objects, each containing nested arrays. I need to flatten these nested arrays into a single flat list. Here's a simplified version of my service code: ```typescript import { Injectable } from '@angular/core'; import { HttpClient } from '@angular/common/http'; import { Observable } from 'rxjs'; import { map } from 'rxjs/operators'; interface Order { id: number; items: string[]; } @Injectable({ providedIn: 'root' }) export class DataService { constructor(private http: HttpClient) {} getAllItems(): Observable { return this.http.get('/api/orders').pipe( map(ord