threshold-ui/ui/core/mirage/serializers/group.js

import ApplicationSerializer from './application';
import { underscore } from '@ember/string';

export default ApplicationSerializer.extend({
  modelName: 'group',

  keyForRelationshipIds(relationshipName) {
    return `${this._container.inflector.singularize(
      underscore(relationshipName)
    )}_ids`;
  },

  _hashForModel(model) {
    const json = ApplicationSerializer.prototype._hashForModel.apply(this, arguments);
    if (model.memberIds.length) json.member_ids = model.memberIds;
    return json;
  }

});