error property subscribe doesn’t exist on type void when sub

Question

I work on angular 7 app I face error property subscribe doesn't exist on type

void when subscribe data from service .

My data static as below on service for test

allReportCategories:any[];
ngOnInit() {


       this._displayreport.getallReportCategories().subscribe((data: any[]) => {
        this.allReportCategories = data;

      });
}

on display report service ts

allReportCategories:any[];


getallReportCategories(){

    return

     this.allReportCategories=[
    {
        "reportCategoryID": 1,
        "reportCategory": "Dashboard Parametric",
        "isDeleted": false,
        "menuIcon": "icon-home"
    },
    {
        "reportCategoryID": 2,
        "reportCategory": "Monitor Reports",
        "isDeleted": false,
        "menuIcon": "icon-list"
    },
    {
        "reportCategoryID": 3,
        "reportCategory": "Other Reports",
        "isDeleted": false,
        "menuIcon": "icon-docs"
    },
    {
        "reportCategoryID": 4,
        "reportCategory": "PCN Flow",
        "isDeleted": false,
        "menuIcon": "icon-list"
    },
    {
        "reportCategoryID": 5,
        "reportCategory": "Compliance By Document",
        "isDeleted": false,
        "menuIcon": "icon-home"
    }
];

  }

sample exist on stackbliz as below :

https://stackblitz.com/edit/create-1arrvm?file=app%2Fdisplayreport.service.ts