async delete({ refresh } = {}) {
    if (!this.__persisted) {
      return;
    }

    await global.kuzzle.internalIndex.delete(
      this.constructor.collection,
      this._id,
      { refresh },
    );

    await this._afterDelete();

    this.__persisted = false;
  }
Delete the current instance from the database.
 - call the _afterDelete hook after deletion

@param {Object} options - refresh (undefined)

@returns {Promise}