notion-sdk-py: in query empty start_cursor option throws error

hi,

I try to make a query:

next_cursor = None
results = notion.databases.query(
        **{
            "database_id": DB_GMB_ID,
            "start_cursor": next_cursor
        }
    )

I receive the error:

APIResponseError: body failed validation: body.start_cursor should be a string or `undefined`, instead was `null`.

“” produces the same result.

What value should be used to satisfy undefined start_cursor?