WordPress enqueue styles by template

child_theme_template_enqueue_styles.php

<?php
/*** 
 From: https://developer.wordpress.org/reference/functions/wp_enqueue_style/
 This is a conditional loading of css file by page template (css will be loaded on on the pages with template-name.php).
 You can change the condition to others. The code should be used in your theme’s function.php.
 Notice: The code works for child themes. If you want to use it in a parent theme replace get_stylesheet_directory_uri() with get_stylesheet_uri().
 **/
$handle = 'wpdocs';
wp_register_style( $handle, get_stylesheet_directory_uri().'/relative/path/to/stylesheet.css', array(), '', true );
if ( is_page_template( 'template-name.php' ) ) {
    wp_enqueue_style( $handle );
}
?>