How to call an embedded Python script

Please help, I am getting nuts. I fail to take the first step as a newbe.

My goal and first step is to use Python in HA. For that I created a Button in the main panel. I found its script editor and made my button to work.

type: button
entity: input_button.trigger_python_script
tap_action:
  action: toggle

The button keeps pressed and I guess that is what is expected. Then I added the sample script from AlexxIT in the same yaml:

script:
  test_source:
    sequence:
      - service: python_script.exec
        data:
          title: Python inline test
          source: |
            import requests
            r = requests.get('https://api.ipify.org?format=json')
            resp = r.json()
            logger.warning(resp)
            hass.services.call('persistent_notification', 'create', {
              'title': data['title'],
              'message': f"My IP: { resp['ip'] }"
            })

Question: How do I change my button so that it calls the embedded script correctly and how can I check its workings. Note that the log entry is of the level warning so I expect it to show in my log

And yes, I did enter python_script: # no S at the end! in configuration.yaml. I got the message that my python dir was missing. That vanished after downloading PythonScriptPro and replacing the standard Python using HACS. My HA runs in docker and is of latest.