是否可以在Objection js中获取子子查询的总计数？

const { Model } = require('objection');

class ParentModel extends Model {
  static get tableName() {
    return 'parent_table';
  }

  static get relationMappings() {
    return {
      children: {
        relation: Model.HasManyRelation,
        modelClass: ChildModel,
        join: {
          from: 'parent_table.id',
          to: 'child_table.parentId'
        }
      }
    };
  }

  static async getParentWithChildCount() {
    const parentWithChildCount = await ParentModel.query()
      .select('parent_table.*')
      .select(ChildModel.query().count().as('childCount'))
      .joinRelated('children')
      .groupBy('parent_table.id');

    return parentWithChildCount;
  }
}

class ChildModel extends Model {
  static get tableName() {
    return 'child_table';
  }
}

(async () => {
  const parents = await ParentModel.getParentWithChildCount();
  console.log(parents);
})();