getSelectTenantUiHiddenCallback() {
    return /** @type {?function()} */ (
        this.getCallbacks_()['selectTenantUiHidden'] || null);
  }
Returns the selectTenantUiHidden callback. It is triggered when the
select provider UI is hidden.
@return {?function()} The selectTenantUiHidden callback, null if not
    available.