Page region CSS class not applied I am working with Drupal 8.5-x, I am trying to render HTML with bootstrap classes, but I am having trouble. Here is my problem:

I have highlighted (region) and content (region). I am trying to add a &lt;section class="col-sm-12 col-md-12"&gt; with highlighted region but to no avail.

I have:

{# Highlighted #}
  {%
    set highlighted_classes = [
      page.sidebar_first and page.sidebar_second ? 'col-sm-6',
      page.sidebar_first and page.sidebar_second is empty ? 'col-sm-9 col-md-8',
      page.sidebar_second and page.sidebar_first is empty ? 'col-sm-12',
      page.sidebar_first is empty and page.sidebar_second is empty ? 'col-sm-12'
    ]
  %}

{# Content #}
  {%
    set content_classes = [
      page.sidebar_first and page.sidebar_second ? 'col-sm-6',
      page.sidebar_first and page.sidebar_second is empty ? 'col-sm-12 col-md-12',
      page.sidebar_second and page.sidebar_first is empty ? 'col-sm-12',
      page.sidebar_first is empty and page.sidebar_second is empty ? 'col-sm-12'
    ]
  %}

  &lt;section {{ highlighted_attributes.addClass(highlighted_classes) }}&gt; 
  &lt;section {{ content_attributes.addClass(content_classes) }}&gt;


when rendered, I get

&lt;section&gt;
&lt;section class="col-sm-12 col-md-12&gt; 


but I was expecting

&lt;section class="col-sm-12 col-md-12"&gt;
&lt;section class="col-sm-12 col-md-12"&gt;


I am lost as to where I could have gone wrong.
My info file is as follows:

    regions:
  navigation: 'Navigation'
  navigation_collapsible: 'Navigation (Collapsible)'
  header: 'Top Bar'
  highlighted: 'Highlighted'
  help: 'Help'
  content: 'Content'
  sidebar_first: 'Primary'
  sidebar_second: 'Secondary'
  footer_first: 'First Footer'
  footer_second: 'Second Footer'
  footer_third: 'Third Footer'
  footer_fourth: 'Fourth Footer'
  footer_fifth: 'Fifth Footer'
  page_top: 'Page top'
  page_bottom: 'Page bottom'


Any help?
Nevermind I read on attributes: https://www.drupal.org/docs/8/theming-drupal-8/using-attributes-in-templates 

The attribute I was referencing 'highlighted_attributes' was blank. I just added a simpler solution, by referecing to the example of the API:

{% set classes = [ 'red', 'green', 'blue' ] %}

&lt;div{{ attributes.addClass(classes) }}&gt;&lt;/div&gt;