SublimeText API - shifting the region position? - plugins

Question

This has been super annoying because it's the last thing that needs to be fixed before the Sublime plugin is ready.
An HSLa converter. The goal is to do this, example:
Before:
color : #000;
After (intended):
color: #000;
color : hsla(...);
But I get this:
color : hsla(...);
color: #000;
Wrong order.
The routine:
duplicate the original region.
insert the converted hsla equivalent.
But it is referencing the original region position, so the inserted HSLa always ends up first. It needs to end up second since the HEX should come first as a CSS fallback.
I need to shift the region either down before inserting. Not clear from the Sublime API how to do this. Or if you have another solution?
Tnx, help appreciated.
----------- code --------
for region in selection:
if not region.empty():
line = self.view.line(region)
line_str = '\n' + self.view.substr(line) // HEX/RGB fallback
self.view.insert(self.edit, line.end(), line_str)
word = self.view.substr(region)
css_hsl = convert_to_hsl(word,force_alpha) // HSLa equivalent
if isinstance(css_hsl, str):
self.view.replace(self.edit, region, css_hsl)