def extend(self, cells: int) -> "Span":
        """Extend the span by the given number of cells.

        Args:
            cells (int): Additional space to add to end of span.

        Returns:
            Span: A span.
        """
        if cells:
            start, end, style = self
            return Span(start, end + cells, style)
        else:
            return self
Extend the span by the given number of cells.

        Args:
            cells (int): Additional space to add to end of span.

        Returns:
            Span: A span.
        
rich/text.py