def split(self, offset: int) -> Tuple["Span", Optional["Span"]]:
        """Split a span in to 2 from a given offset."""

        if offset < self.start:
            return self, None
        if offset >= self.end:
            return self, None

        start, end, style = self
        span1 = Span(start, min(end, offset), style)
        span2 = Span(span1.end, end, style)
        return span1, span2
Split a span in to 2 from a given offset.
rich/text.py