setCollapsed(collapsed) {
    this.userCollapsed_ = collapsed;
    if (!this.collapsible_ || this.collapsed_ === collapsed) {
      return;
    }
    this.handleToggle_();
  }
Collapse or expand the attribution according to the passed parameter. Will
not do anything if the attribution isn't collapsible or if the current
collapsed state is already the one requested.
@param {boolean} collapsed True if the widget is collapsed.
@api