Update subitem text

I try to update a subitem Text with the API.
This is my code:

  updateChange = f'mutation {{ change_simple_column_value (item_id: 5570607428, board_id: 5548784580, column_id:"text", value: "test") {{ id }} }}'
  data = {'query': updateChange}
  r = requests.post(url=apiUrl, json=data, headers=headers) 

And this is my output:

{‘error_code’: ‘ResourceNotFoundException’, ‘status_code’: 404, ‘error_message’: ‘Item not found in board’, ‘error_data’: {‘resource_type’: ‘item’, ‘item_id’: 5570607428, ‘pulse_id’: 5570607428, ‘board_id’: 5548784580, ‘error_reason’: None}}

After some research, i found out that each item has unique subitem ID, so this error appears cause i putted the main board id in board_id instead of the unique subitem board id.

How can i fix that?

I succeed to get the subitem board id by running this function:

 test = f'''
        query {{
            boards(ids: 5548784580) {{
                columns(ids: "subitems"){{
 data = {'query': test}
 r = requests.post(url=apiUrl, json=data, headers=headers)  # make request
 response = r.json()

And this is my ouyput:

{‘data’: {‘boards’: [{‘columns’: [{‘settings_str’: ‘{“displayType”:“BOARD_INLINE”,“itemTypeName”:“column.subtasks.title”,“allowMultipleItems”:true,“boardIds”:[5548784646]}’}]}]}, ‘account_id’: 6084643}

But when i try to run this code on different board, I get this output

{‘data’: {‘boards’: [{‘columns’: }]}, ‘account_id’: 6084643}

What is the difference?

Does the other board have any subitems? If the other board has never had a subitem created, then a subitem board and subitems column do not yet exist.