Problem downloading file from dropbox

Hi all ,

I can't get this to work:
(part of a python class)

def download_file(self, source_file):
    "Download a file from Dropbox"
    print('Start Dropbox download')
    with open(source_file, "wb") as f:
        metadata, res = self.dbx.files_download(path='F:/Profielmap/Downloads/DropboxToken.txt')
        f.write(res.content)

I get error: dropbox did not match pattern
The file should be downloaded in F:/Profielmap/Downloads, tried changing slashes , going through a variable, i keep getting syntax errors about not matching any patteren ,why is this so hard to find ?? ;-)
When i use path="/DropboxToken.txt" the file downloads in F:

Cheers ,John