media_additional_owners not working

[correo....@gmail.com]

Hello everyone, I have a problem with the api.
When I do:

api.PostUpdate(status=text, media=media, media_additional_owners=owners_list)

It produces the following error

  File "C:\Program Files\Python35\lib\site-packages\twitter\api.py", line 1096, in PostUpdate
    media_ids.append(self.UploadMediaSimple(media, media_additional_owners))
  File "C:\Program Files\Python35\lib\site-packages\twitter\api.py", line 1145, in UploadMediaSimple
    resp = self._RequestUrl(url, 'POST', data=parameters)
  File "C:\Program Files\Python35\lib\site-packages\twitter\api.py", line 4965, in _RequestUrl
    resp = requests.post(url, files=data, auth=self.__auth, timeout=self._timeout, proxies=self.proxies)
  File "C:\Program Files\Python35\lib\site-packages\requests\api.py", line 110, in post
    return request('post', url, data=data, json=json, **kwargs)
  File "C:\Program Files\Python35\lib\site-packages\requests\api.py", line 56, in request
    return session.request(method=method, url=url, **kwargs)
  File "C:\Program Files\Python35\lib\site-packages\requests\sessions.py", line 461, in request
    prep = self.prepare_request(req)
  File "C:\Program Files\Python35\lib\site-packages\requests\sessions.py", line 394, in prepare_request
    hooks=merge_hooks(request.hooks, self.hooks),
  File "C:\Program Files\Python35\lib\site-packages\requests\models.py", line 297, in prepare
    self.prepare_body(data, files, json)
  File "C:\Program Files\Python35\lib\site-packages\requests\models.py", line 455, in prepare_body
    (body, content_type) = self._encode_files(files, data)
  File "C:\Program Files\Python35\lib\site-packages\requests\models.py", line 152, in _encode_files
    fdata = fp.read()
AttributeError: 'int' object has no attribute 'read'

Note that if I omit the media_additional_owners argument it works perfectly and if I try to add the owners through the UploadMediaSimple method it also produces the same error.

Thank you in advance.
-Ángel