During the upload you may monitor its progress using a progress bar. Once uploaded,
the files are spooled to temporary files at the server. You may
configure the control to allow the selection of multiple files
at once, for more recent browsers that support this. The client
filenames, the temporary spool file names, and the content types
can be inspected for each uploaded file when the upload was
completed.
File uploads can be started in the background by connecting the
changed() signal to the upload() function.