angular input and output in the same variable

<p>home-layout works!</p>
<app-tooltip [(doubleBinding)]="this.parentVal"></app-tooltip>
<div>PARENT:{{parentVal}}</div>

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

@Component({
  selector: 'app-home-layout',
  templateUrl: './home-layout.component.html',
  styleUrls: ['./home-layout.component.css']
})
export class HomeLayoutComponent implements OnInit {
  parentVal: string = 'HI';
  constructor() { }
  ngOnInit() {
  }
}

<p>tooltip works!</p>
<div>
    CHILD:{{doubleBinding}}
</div>
<button (click)="go()">GO</button>

import { Component, OnInit, Output, Input, EventEmitter } from '@angular/core';

@Component({
  selector: 'app-tooltip',
  templateUrl: './tooltip.component.html',
  styleUrls: ['./tooltip.component.css']
})
export class TooltipComponent implements OnInit {
  @Input() doubleBinding: string = '';
  @Output() doubleBindingChange: EventEmitter<string> = new EventEmitter<string>();
  constructor() { }
  ngOnInit() {
  }
  go() {
    this.doubleBindingChange.emit('GO CLICK!!!!');
  }
}