ember data included issue

adapters.application.js

import Adapter from "ember-data/adapters/json-api";

export default Adapter.extend();

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
	actions: {
    loadData: function() {
      let store = this.get("store");
      let json = {
        data: {
          id: "1",
          type: "child",
          attributes: {
            id: "1",
            name: "child1"
          },
          relationhips: {
            parent: {
              type: "adult",
              id: "2"
            }
          },
        },
        included: [
          {
            id: "2",
            type: "adult",
            attributes: {
              id: "2",
              name: "parent"
            },
            relationships: {
              type: "children",
              children: [{id: "1", type: "child"}]
            }
          },
          {
            id: "1",
            type: "child",
            attributes: {
              id: "1",
              name: "child1"
            },
            relationships: {
              parent: {
                id: "2",
                type: "parent"
              }
            }
          }
        ]
      }
      store.push(json)
      console.log(store.peekAll("child").toArray())
      console.log(store.peekAll("adult").toArray()[0].get("children").toArray())
    }
  }
});

models.adult.js

import Model from 'ember-data/model';
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
  children: hasMany("children"),
  name: attr("string")
});

models.child.js

import Model from 'ember-data/model';
import attr from 'ember-data/attr';
import { belongsTo, hasMany } from 'ember-data/relationships';

export default Model.extend({
  parent: belongsTo("adult"),
  name: attr("string")
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<button {{action "loadData"}}>
 Press this
</button>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "2.13.0",
    "ember-template-compiler": "2.13.0",
    "ember-testing": "2.13.0"
  },
  "addons": {
    "ember-data": "2.13.2"
  }
}