setCollapsible(collapsible) {
    if (this.collapsible_ === collapsible) {
      return;
    }
    this.collapsible_ = collapsible;
    this.element.classList.toggle('ol-uncollapsible');
    if (!collapsible && this.collapsed_) {
      this.handleToggle_();
    }
  }
Set whether the overview map should be collapsible.
@param {boolean} collapsible True if the widget is collapsible.
@api