protected static function getUniqueFilePath( $startingPath = '' ) {
        if ( file_exists( $startingPath ) ) {
            $filename_ext = pathinfo( $startingPath, PATHINFO_EXTENSION );
            $startingPath = preg_replace( '/^(.*)\.' . $filename_ext . '$/', '$1_' . date( 'YmdHis' ) . '.' . $filename_ext, $startingPath );

            if ( is_null( $startingPath ) ) {
                throw new \Exception( "The php function preg_replace (called in Excel::getUniqueFilePath()) returned null, indicating an error." );
            }
        }

        return $startingPath;
    }