WordPress-如何获得用户以简码给出的价值?

I just want to display posts by number value by user given in "pocet" parameter [oblubene-clanky pocet=""]. This code isn't working. I tried and edited this solution with no results. So, what is wrong?

function my_shortcode( $atts ) { ?>
    <div class="list_posts mt-5">

    <?php       
    $atts = shortcode_atts( array( 'pocet' => '' ), $atts, 'oblubene-clanky' );
    $args = array(
        'posts_per_page' => $atts['pocet'],
        'orderby' => 'date',
        'order' => 'DESC',
    );
    $query = new WP_Query( $args );

    if ( $query->have_posts() ) :
        while ( $query->have_posts() ) : $query->the_post(); 
            if ( isset( $atts['pocet'] ) ) : ?>

                <div class="pb-4 d-flex ">
                    <div id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
                        <a href="<?php the_permalink(); ?>"><img src="<?php echo get_the_post_thumbnail_url( get_the_ID(), 'thumbnail' ); ?>" alt="<?php the_title(); ?>"></a>
                    </div>

                    <div class="pl-5">
                        <h6><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h6>
                        <p><?php the_excerpt(); ?></p>
                        <p class="small m-0"><?php echo get_the_date(); ?></p>
                    </div>          
                </div>

            <?php
            endif;
        endwhile;
        wp_reset_postdata();
    endif; ?>

    </div>

<?php
}
add_shortcode( 'oblubene-clanky', 'my_shortcode' );