How to add custom post type in the where argument to fetch data?

[ankur-astra]

I have created a post type called LearnArticles in wordpress and another post type Learn Categories. Now I have linked both of them and I can access the Learn Categories data under the Learn Articles. But when I am trying to fetch data of a particular category I am unable to find the Learn Categories field in the Where attribute of the Learn Articles. How can I populate the LearnCategory field in the where argument of the Learn Article?

Things I have tried:
Registering a new taxonomy and connecting it with the learn category field:

function register_custom_taxonomy() {
     $args = array(
       // other arguments
       'labels'  => array(
         'menu_name' => __( 'Learn Categories' ),
       ),
       'show_in_graphql' => true,
       'graphql_single_name' => 'LearnCategory',
       'graphql_plural_name' => 'LearnCategories',
     );
     register_taxonomy('learn_category', 'learn_article', $args);
   }
   add_action('init', 'register_custom_taxonomy');