Trying to create color font with muktiple ligature substitution

[havealoha]

First I tried with FontForge but found that it does not support color emoji. So Im trying my hand at fonttools...

I want to create a font that substitutes all punycodes "xn--e28h" with their equivalant emoji "😀" I would create a table or array used by the python script instead of trying to rely on parsing noto-emoji.ttf or idna tools. Here was my attempt at a proof of concept but it didnt work (error at bottom). Can anyone steer me in the right direction?

from fontTools.ttLib import TTFont
from fontTools.unicode import Unicode
from fontTools.varLib.builder import addOpenTypeLigature

# Create a new font
font = TTFont()

# Define ligature glyph data
ligature_name = "xn--e28h"

#not sure if this is right, maybe need "U+000A U+1F600" or ?
ligature_unicode = [0x1F604]  # Unicode code point for the smiley face emoji

# Create a ligature glyph
ligature_glyph = font.getGlyphSet().get(ligature_name)
ligature_glyph.width = 1000

# Update cmap and GSUB tables
font["cmap"].tables[0].addMapping(Unicode(*ligature_unicode), ligature_name)

# Create a GSUB lookup for ligature substitution
gsub_table = font.getGSUB()
lookup = gsub_table.table.LookupList.Lookup[0]  # Replace with the appropriate lookup index
addOpenTypeLigature(lookup, ligature_name, ['x', 'n', '-', '-', 'e', '2', '8', 'h'])

# Save the font
font.save("punycode.otf")

Error:

python3 emoji4.py 
Traceback (most recent call last):
  File "/home/punycode.py", line 3, in <module>
    from fontTools.varLib.builder import addOpenTypeLigature
ImportError: cannot import name 'addOpenTypeLigature' from 'fontTools.varLib.builder' (/usr/local/lib64/python3.12/site-packages/fontTools/varLib/builder.py)