favicon-[layer].svg.py

#!/usr/bin/env python3
import xml.etree.ElementTree as ET
from sys import argv, stdin, stdout

layer = argv[1]
doc = ET.parse(stdin)
root = doc.getroot()

for g in root.findall(".//{http://www.w3.org/2000/svg}g[@id]"):
    id = g.get("id")
    if id and id.startswith("layer-") and id not in {"layer-base", f"layer-{layer}"}:
        root.remove(g)

doc.write(stdout, encoding = "unicode", xml_declaration = True)

doesn't preserve formatting, namespace names, etc. so less helpful than the alternative yq + jq approach.