Trouble generating a model instance and applying it to a specific key in Ember Mirage

While generating an instance of a staffMember within ember-cli-mirage I'm attempting to create a 'task' and assign it to the key 'tasksCreated' within the staffMember model. My current code is as follows;

It's creating a task, and creating a staffMember but the two have no relationships built between them.

app/models/staff-member.js

import DS from 'ember-data';

export default DS.Model.extend({
    name: DS.attr('string'),
    atWork: DS.attr('boolean'),
    avatar: DS.attr(),
    tasksCreated: DS.hasMany('task', {
        inverse: 'creator'
    }),
    tasksAssigned: DS.hasMany('task', {
        inverse: 'assignee'
    })
});

app/models/tasks.js

import DS from 'ember-data';

export default DS.Model.extend({
    creator: DS.belongsTo('staff-member', { inverse: null }),
    assignee: DS.belongsTo('staff-member', { inverse: null }),
    creationDate: DS.attr(),
    description: DS.attr('string'),
    urgency: DS.attr()
 });

mirage/models/staff-member.js

import {Model, hasMany} from 'ember-cli-mirage';

export default Model.extend({
    tasksCreated: hasMany('task'),
    tasksAssigned: hasMany('task', { inverse: 'assignee'})
});

mirage/models/task.js

import {Model, belongsTo} from 'ember-cli-mirage';

export default Model.extend({
    creator: belongsTo('staff-member'),
    assignee: belongsTo('staff-member')
});

mirage/factories/staff-member.js

import { Factory, faker, trait } from 'ember-cli-mirage';

export default Factory.extend({
    name: faker.name.firstName,
    atWork: faker.random.boolean,
    avatar: faker.image.avatar,
    withTasks: trait({
        afterCreate(staffMember, server){
            server.createList('task',2,{tasksCreated: [staffMember]});
        }
    })
});

mirage/factories/task.js

import { Factory, faker } from 'ember-cli-mirage';

export default Factory.extend({
    creationDate: faker.date.recent,
    description: faker.lorem.sentence,
    urgency: faker.random.number({
        'min': 0,
        'max': 4
    })
});

mirage/scenarios/default.js

export default function(server ) {  

    server.createList('staff-member', 4, 'withTasks');

}