why is the function name not right

im following this page : https://learn.projectdmc.org/lesson/action-hooks/

but when I put that code in the functions.php of the twentytwentyfour theme I see this error message:

Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, function “wp_learn_setup_theme” not found or invalid function name in C:\laragon\www\learn\wp-includes\class-wp-hook.php:324 Stack trace: #0 C:\laragon\www\learn\wp-includes\class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array) #1 C:\laragon\www\learn\wp-includes\plugin.php(517): WP_Hook->do_action(Array) #2 C:\laragon\www\learn\wp-settings.php(673): do_action(‘after_setup_the…’) #3 C:\laragon\www\learn\wp-config.php(103): require_once(‘C:\\laragon\\www\\…’) #4 C:\laragon\www\learn\wp-load.php(50): require_once(‘C:\\laragon\\www\\…’) #5 C:\laragon\www\learn\wp-blog-header.php(13): require_once(‘C:\\laragon\\www\\…’) #6 C:\laragon\www\learn\index.php(17): require(‘C:\\laragon\\www\\…’) #7 {main} thrown in C:\laragon\www\learn\wp-includes\class-wp-hook.php on line 324
`</p>

<p></p>

<p>What went wrong here ?</p>