Custom shortcode w wordpress

function register_shortcodes(){

  add_shortcode( 'w_code', 'display_code' );
  function display_code(){
    return "Some value";
  }
}  

add_action( 'init', 'register_shortcodes' );

function wporg_shortcode( $atts = [] ) {

  $wporg_atts = shortcode_atts(
      array(
          'q' => 0,
      ), $atts
  );
  $o = "";
  $o .= esc_html__( $wporg_atts['q'], 'wporg' );
  return $o;
}


function wporg_shortcodes_init() {
  add_shortcode( 'wporg', 'wporg_shortcode' );
}

add_action( 'init', 'wporg_shortcodes_init' );

function register_shortcodes(){
    add_shortcode( 'w_ebooks', 'display_code' );

    function display_code(){
      $ret = "";
      $ret .= '<div class="container xl">';
      $ret .= '<div class="ebooks_section_w">';
      
      $args = array(
        'post_type' => 'post',
        'category_name' => 'ebook',
        'post_status' => 'publish',
        'order'=>'ASC'
        );
    $the_query = new WP_Query($args);
    if($the_query -> have_posts()){
        while($the_query -> have_posts()){
            $the_query -> the_post();
            $ret .= '<div class="ebook_item_w">';
            $ret .= '<a href="'.get_the_permalink().'">';
            if ( has_post_thumbnail() ) {
              $ret .= get_the_post_thumbnail();
            }
            
            $ret .= '</a>';
            $ret .= '<h2 class="ebook_title"><a href="'.get_the_permalink().'">'.get_the_title().'</a></h2>';
            $ret .= '<p>'.substr(get_the_excerpt(), 0, 200).'...</p>';
  
            $ret .= '</div>'; // end ebook_item_w
        }
    }
        
    wp_reset_postdata();
    $ret .= '</div>'; //end ebooks_section_w
    $ret .= '</div>';//end container
  
    return $ret;
    } 
  } 
  add_action( 'init', 'register_shortcodes' );