gistfile1.txt

function gloria_publish_video_gallery() {

    ob_start() ;

    // $test_string = '<h1>Got To Test String</h1>' ;
      //  echo $test_string ;

    $test_string = include (get_stylesheet_directory() . '/inc/buzz-slideshow-videos-gallery-template.php');
    // echo "<h1>the other test string</h2>" ;
    echo $test_string ;
    
    return  ob_get_clean() ;

}

add_shortcode( 'gloria_video_gallery', 'gloria_publish_video_gallery' );

// included template:

<?php

return  '<h1>Testing output from shortcode</h1>' ;

?>