title: Find records that are not associated with other model in HABTM
body: <p>I have two models 'Article' and 'List' both associated with HABTM association. I also have 'articles_lists' join table that has 'article_id' and 'list_id'. Now I would like to display all the articles that are not associated with any lists. Which is articles which does not have entry in 'articles_lists' table.</p>
  
  <p>How can I achieve this in Rails 5. Please help</p>