Contact Form 7 (CF7) - load JS & CSS only when it is necessary

cf7_load_js_css.php

<?php
/**
 * CF 7 - version 5.4.1 
 * Load JS & CSS only when necessary
 * 
 * Use WP functions '__return_true', '__return_false' to load the
 * necessary files. The 'is_page()' should be called after the init
 * hook and the js+css must be enqueued before the wp_head hook.
 * 
 */
 
add_filter( 'wpcf7_load_js', '__return_false' );
add_filter( 'wpcf7_load_css', '__return_false' );

function fm_cf7_activate_scripts() {
	if (is_page('contact') || is_page('45') || is_singular( array( 'cd', 'book' ) )) {
		add_filter( 'wpcf7_load_js', '__return_true' );
		add_filter( 'wpcf7_load_css', '__return_true' );
	}
}

add_action( 'get_header', 'fm_cf7_activate_scripts' );