Insert Custom CSS into All Landing Page Custom Post Types

<?php 
// Insert Custom Styles on all landing pages. Insert in themes function.php file
add_action( 'wp_head', 'custom_landing_page_styles' );
 
function custom_landing_page_styles() {
global $post;
if (isset($post)&&$post->post_type=='landing-page') { ?>
 
   <style type="text/css">
   /* Your Landing Page Specific CSS here */
    #css_selection { display: none !important; }
   </style>
    
<?php } 
}