analytics-1.4-apis data-sources-api

Hi,
we're using the data-sources-api of analytics-1.4-apis and we got this error: "invalid columns, at least one is required and columns must match for each upload" when we try to use DataSources.UploadData.

We using python 3.7 with the requests library.

As required by the APi ( sees the doc ), on the post request  we define the columns parameter as array of string:

columns = ["Date", "Evar 96", "Event 97", "Event 99", "Event 98", "Event 100"]
rows = [
    ["12/31/2020", "100011173", "1", "2", "3", "4"],
    ["01/29/2021", "100011173", "1", "3", "4", "5"],
    ["01/30/2021", "100011173", "2", "6", "5", "6"],
    ["01/31/2021", "100011173", "3", "4", "5", "6"],
    ["02/01/2021", "100011173", "4", "5", "6", "7"],
]

and give it to the API as item of the payload:

payload = {
"columns": columns,
"dataSourceID": dataSourceID,
"finished": True,
"jobName": "pippo123",
"reportSuiteID": rsid,
"rows": rows
}

url = "https://api.omniture.com/admin/1.4/rest/?method="
response = requests.post(url + "DataSources.UploadData", headers=header, data=payload)

Now we don't undertand because we got the error?

Thanks, Stefano G.