all() {
      const collection = this.constructor.collection();
      collection._knex = this.query().clone();
      this.resetQuery();
      if (this.relatedData) collection.relatedData = this.relatedData;
      return collection;
    }
Fired after a `fetch` operation. A promise may be returned from the
event handler for async behaviour.

@event Model#fetched
@tutorial events
@param {Model} model
  The model firing the event.
@param {Object} response
  Knex query response.
@param {Object} options
  Options object passed to {@link Model#fetch fetch}.
@returns {Promise}
  If the handler returns a promise, `fetch` will wait for it to
  be resolved.