post processing gcode retraction

[Johnn 2]

Hi,
I would like to use the firmware retraction of Klipper and generating a retraction tower with Cura with a post-processing script.
The issue is that there is no such already made script with firmware retraction (or custom command).
I tried to understand and adapt some cura scripts post processing gcode (I'm new to this).
I wrote a script but it doesn't work (the script and the parameters are shown in cura, but it don't do anything to the gcode generated by cura), so there should be some errors in the code.
Is there someone here who is knowledgeable about cura scripts ? Thanks. 
Here is the code below :

from ..Script import Script
from UM.Logger import Logger
from UM.Application import Application
import re  # To perform the search
from typing import List, Tuple

__version__ = '1.5.1'

def changement_Z(line: str) -> bool:
    """Check if current line is the start of a layer section.
    Args:
        line (str): Gcode line
    Returns:
        bool: True if the line is the start of a layer section
    """
    return "G0" in line and "Z" in line

class a_MYRETRACTTOWER(Script):
    def __init__(self):
        super().__init__()

    def getSettingDataString(self):
        return """{
            "name": "a_MYRETRACTTOWER",
            "key": "a_MYRETRACTTOWER",
            "metadata": {},
            "version": 2,
            "settings":
            {
                "debut_ret":
                {
                    "label": "Starting retraction value",
                    "description": "the starting value of the Tower retraction.",
                    "type": "float",
                    "default_value": 0.1
                },
                "inc_ret":
                {
                    "label": "Increment",
                    "description": "the value of increment retraction",
                    "type": "float",
                    "default_value": 0.2
                },
                "debut_hauteur":
                {
                    "label": "Starting retraction height",
                    "description": "the starting value of the Tower retraction.",
                    "type": "float",
                    "default_value": 1
                },
                "inc_hauteur":
                {
                    "label": "height by retraction",
                    "description": "the value height before incrementing retraction",
                    "type": "float",
                    "default_value": 5
                }
            }
        }"""
    def execute(self, data):
        debut_ret = self.getSettingValueByKey("debut_ret")
        inc_ret = self.getSettingValueByKey("inc_ret")
        debut_hauteur = self.getSettingValueByKey("debut_hauteur")
        inc_hauteur = self.getSettingValueByKey("inc_hauteur")
        temporaire_data = []
        i = 0
        ret = debut_ret
        for line in data:
            hauteur_cible = debut_hauteur + i*inc_hauteur
            temporaire_data = temporaire_data.append(line)
            if not "G0" in line or not "Z" in line:
                continue
            hauteur_line = self.getValue(line, "Z")
            if hauteur_line < hauteur_cible:
                continue
            insertion_code = "MY_RETRACTION_TOWER RETRACT_LENGTH="+str(ret)
            temporaire_data = temporaire_data.append(insertion_code)
            i = i + 1
            ret = debut_ret + i * inc_ret
        data = temporaire_data
        return data

Edited April 24, 2022 by Johnn