如何在angular 6中更改拦截器中的内容类型？

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable()
export class ContentTypeInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    // 修改请求的内容类型为application/json
    const modifiedReq = req.clone({
      setHeaders: {
        'Content-Type': 'application/json'
      }
    });

    return next.handle(modifiedReq);
  }
}

import { NgModule } from '@angular/core';
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
import { ContentTypeInterceptor } from './content-type.interceptor';

@NgModule({
  imports: [HttpClientModule],
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: ContentTypeInterceptor,
      multi: true
    }
  ]
})
export class AppModule { }

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable()
export class DataService {
  constructor(private http: HttpClient) { }

  getData(): Observable<any> {
    return this.http.get<any>('https://api.example.com/data');
  }
}