Move sidebar from right to left

I need to move the right sidebar to the left. I’ve tried:

1) Changing the class from right to left by adding the following to the child theme’s functions.php:

/**
* Layout classes
* Adds ‘right-sidebar’ and ‘left-sidebar’ classes to the body tag
* @param array $classes current body classes
* @return string[] modified body classes
* @since 1.0.0
*/
function storefront_layout_class( $classes ) {
$layout = get_theme_mod( ‘storefront_layout’ );

if ( ” == $layout ) {
$layout = ‘left’;
}

$classes[] = $layout . ‘-sidebar’;

return $classes;
}

Result:
Fatal error: Cannot redeclare storefront_layout_class() (previously declared in /foo/functions.php:35) in /foo/functions.php on line 101

2) Removing and re-adding storefront_sidebar in child theme’s functions.php, along with above code. I tried adding to 0, 10, and 20 in turn. Each produced the same results.

Result: same error as above

What’s the proper way to accomplish this task?