Plugin administration menu bug

Hello, I’m trying to build a plugin.
I used the wordpress codex code to test adding menus in adminisatration panel.
But there’s a problem :

Fatal error: Cannot redeclare mt_add_pages() (previously declared in /home/***/wp-content/plugins/wp-fetchamovie/wp-fetchamovie.php:16) in /home/***/wp-content/plugins/wp-fetchamovie/wp-fetchamovie.php on line 16

I only declared it once…

Here’s the code (https://codex.www.ads-software.com/Adding_Administration_Menus) :

<?php
/*
Plugin Name: Menu Test
Plugin URI: https://www.ads-software.com
Description: Menu Test
Author: Nobody
Author URI: https://example.com
*/

// Hook for adding admin menus
add_action('admin_menu', 'mt_add_pages');

// action function for above hook
function mt_add_pages() {
    // Add a new submenu under Options:
    add_options_page('Test Options', 'Test Options', 8, 'testoptions', 'mt_options_page');

    // Add a new submenu under Manage:
    add_management_page('Test Manage', 'Test Manage', 8, 'testmanage', 'mt_manage_page');

    // Add a new top-level menu (ill-advised):
    add_menu_page('Test Toplevel', 'Test Toplevel', 8, __FILE__, 'mt_toplevel_page');

    // Add a submenu to the custom top-level menu:
    add_submenu_page(__FILE__, 'Test Sublevel', 'Test Sublevel', 8, 'sub-page', 'mt_sublevel_page');

    // Add a second submenu to the custom top-level menu:
    add_submenu_page(__FILE__, 'Test Sublevel 2', 'Test Sublevel 2', 8, 'sub-page2', 'mt_sublevel_page2');
}

// mt_options_page() displays the page content for the Test Options submenu
function mt_options_page() {
    echo "<h2>Test Options</h2>";
}

// mt_manage_page() displays the page content for the Test Manage submenu
function mt_manage_page() {
    echo "<h2>Test Manage</h2>";
}

// mt_toplevel_page() displays the page content for the custom Test Toplevel menu
function mt_toplevel_page() {
    echo "<h2>Test Toplevel</h2>";
}

// mt_sublevel_page() displays the page content for the first submenu
// of the custom Test Toplevel menu
function mt_sublevel_page() {
    echo "<h2>Test Sublevel</h2>";
}

// mt_sublevel_page2() displays the page content for the second submenu
// of the custom Test Toplevel menu
function mt_sublevel_page2() {
    echo "<h2>Test Sublevel 2</h2>";
}

?>