Running SNAP script error

Hi I would like to process multiple images in Python with a for loop.

When I try to do it for one file it works, for example:

!gpt "Method/gpt_scripts/s1_cal_deb.xml" -t "result_step1/S1A_IW_SLC__1SDV_20190928T003154_20190928T003221_029214_035175_65FA.zip/s1_cal_deb/S1A_IW_SLC__1SDV_20190928T003154_20190928T003221_029214_035175_65FA.zip_Cal_deb_script.dim" "./Rader Images/S1A_IW_SLC__1SDV_20190928T003154_20190928T003221_029214_035175_65FA.zip"

However I want to do it for many files, so I tested this in Python 3.

deb = (f'"{"Method/gpt_scripts/s1_cal_deb.xml"}"') 
deb = deb + " -t "

url = (f'"{"result_step1/S1A_IW_SLC__1SDV_20190928T003154_20190928T003221_029214_035175_65FA.zip"}')
url5 = (f'{"S1A_IW_SLC__1SDV_20190928T003154_20190928T003221_029214_035175_65FA.zip"}')       
url2 = (f'{"/s1_cal_deb/"}')
url3 = (f'{url5}')
url4 = (f'{"_Cal_deb_script.dim"}"')
source = (f'"{"./Rader Images/S1A_IW_SLC__1SDV_20190928T003154_20190928T003221_029214_035175_65FA.zip"}"')
  
output = url + url2 + url3 + url4

final = deb + output + " " + source
        
final

Output:

'"Method/gpt_scripts/s1_cal_deb.xml" -t "result_step1/S1A_IW_SLC__1SDV_20190928T003154_20190928T003221_029214_035175_65FA.zip/s1_cal_deb/S1A_IW_SLC__1SDV_20190928T003154_20190928T003221_029214_035175_65FA.zip_Cal_deb_script.dim" "./Rader Images/S1A_IW_SLC__1SDV_20190928T003154_20190928T003221_029214_035175_65FA.zip"'

The final string is exactly the same as the first one. But I get the following error:

INFO: org.esa.snap.core.gpf.operators.tooladapter.ToolAdapterIO: Initializing external tool adapters
INFO: org.esa.snap.core.util.EngineVersionCheckActivator: Please check regularly for new updates for the best SNAP experience.
java.lang.IllegalStateException: Operator SPI not found for operator [final]
	at org.esa.snap.core.gpf.annotations.ParameterDescriptorFactory.getOpSpi(ParameterDescriptorFactory.java:262)
	at org.esa.snap.core.gpf.annotations.ParameterDescriptorFactory.createMapBackedOperatorPropertyContainer(ParameterDescriptorFactory.java:67)
	at org.esa.snap.core.gpf.main.CommandLineTool.convertParameterMap(CommandLineTool.java:400)
	at org.esa.snap.core.gpf.main.CommandLineTool.runOperator(CommandLineTool.java:296)
	at org.esa.snap.core.gpf.main.CommandLineTool.runGraphOrOperator(CommandLineTool.java:284)
	at org.esa.snap.core.gpf.main.CommandLineTool.run(CommandLineTool.java:188)
	at org.esa.snap.core.gpf.main.CommandLineTool.run(CommandLineTool.java:121)
	at org.esa.snap.core.gpf.main.GPT.run(GPT.java:54)
	at org.esa.snap.core.gpf.main.GPT.main(GPT.java:34)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.esa.snap.runtime.Launcher.lambda$run$0(Launcher.java:55)
	at org.esa.snap.runtime.Engine.runClientCode(Engine.java:189)
	at org.esa.snap.runtime.Launcher.run(Launcher.java:51)
	at org.esa.snap.runtime.Launcher.main(Launcher.java:31)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.exe4j.runtime.LauncherEngine.launch(LauncherEngine.java:65)
	at com.exe4j.runtime.WinLauncher.main(WinLauncher.java:101)
	at com.install4j.runtime.launcher.WinLauncher.main(WinLauncher.java:26)

Error: Operator SPI not found for operator [final]

Im a missing something here? How can I fix this please? I am new to using SNAP Toolbox

Many Thanks,

Ish