Cannot Redeclare Function generate_posted_on. Error

I'm trying to create a post updated date schema on my website TheGuideX to show last updated date of a post instead of showing the published date, but when I'm trying to add this file in "Code Snippets" plugin, it is showing "Cannot redeclare function generate_posted_on." error

Code Snippets I Used:

if ( ! function_exists( 'generate_posted_on' ) ) :
/**
 * Prints HTML with meta information for the current post-date/time and author.
 */
function generate_posted_on() 
{	
	$date = apply_filters( 'generate_post_date', true );
	$author = apply_filters( 'generate_post_author', true );
	//if ( get_the_time( 'U' ) !== get_the_modified_time( 'U' ) ) 
		$time_string .= '<time class="updated" datetime="%3$s" itemprop="dateModified">%4$s</time>';
	$time_string = sprintf( $time_string,
		esc_attr( get_the_date( 'c' ) ),
		esc_html( get_the_date() ),
		esc_attr( get_the_modified_date( 'c' ) ),
		esc_html( get_the_modified_date() )
	);
	
	// If our date is enabled, show it
	if ( $date ) :
		printf( '<span style="float: left; margin-right: 3px;">Updated:</span><span class="posted-on">%1$s</span>',
			sprintf( '<a href="%1$s" title="%2$s" rel="bookmark">%3$s</a>',
				esc_url( get_permalink() ),
				esc_attr( get_the_time() ),
				$time_string
			)
		);
	endif;
	
	// If our author is enabled, show it
	if ( $author ) :
		printf( ' <span class="byline">%1$s</span>',
			sprintf( '<span class="author vcard" itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author">%1$s <a class="url fn n" href="%2$s" title="%3$s" rel="author" itemprop="url"><span class="author-name" itemprop="name">%4$s</span></a></span>',
				__( 'by','generatepress'),
				esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ),
				esc_attr( sprintf( __( 'View all posts by %s', 'generatepress' ), get_the_author() ) ),
				esc_html( get_the_author() )
			)
		);
	endif;
	
}
endif;

Edit: "Temporary I solved this problem by using this code in function.php file, but not able to use the same code using Code Snippets"