def write(self, s, tags=(), mark="insert"):
        """Write text to text widget.

        The text is inserted at the given index with the provided
        tags.  The text widget is then scrolled to make it visible
        and updated to display it, giving the effect of seeing each
        line as it is added.

        Args:
            s: Text to insert into text widget.
            tags: Tuple of tag strings to apply on the insert.
            mark: Index for the insert.

        Return:
            Length of text inserted.
        """
        assert isinstance(s, str)
        self.text.insert(mark, s, tags)
        self.text.see(mark)
        self.text.update()
        return len(s)