async _transitionHide({ backdropNode, contentNode }) {
    // `this.transitionHide` is a hook for our users
    await this.transitionHide({ backdropNode, contentNode });
    this._handlePosition({ phase: 'hide' });
    if (!backdropNode) {
      return;
    }
    backdropNode.classList.remove(`overlays__backdrop--animation-in`);
  }
@param {{backdropNode:HTMLElement, contentNode:HTMLElement}} hideConfig
@protected