This gist is used in the tutorial https://www.vijayan.in/how-to-create-custom-table-list-in-wordpress-admin-page

allowed_post_types.php

<?php
...
	/**
	 * Retrieve post types to be shown in the table.
	 *
	 * @return array Allowed post types in an array.
	 */
	private function allowed_post_types() {
		$post_types = get_post_types( array( 'public' => true ) );
		unset( $post_types['attachment'] );

		return $post_types;
	}
...