Change Email Subject for New Collection Email

/**
 * Change the email subject of the email that is sent to the client for a new collection
 */
function my_picu_custom_collection_mail_subject( $collection_title ) {
	return 'Please approve: ' . $collection_title;
}

add_filter( 'picu_collection_mail_subject', 'my_picu_custom_collection_mail_subject' );