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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def format_filename(filename, shorten=False):
 """Formats a filename for user display. The main purpose of this function is to ensure that the filename can be displayed at all. This will decode the filename to unicode if necessary in a way that it will not fail. Optionally, it can shorten the filename to not include the full path to the filename. :param filename: formats a filename for UI display. This will also convert the filename into unicode without failing. :param shorten: this optionally shortens the filename to strip of the path that leads up to it. """

    if shorten:
        filename = os.path.basename(filename)
    return filename_to_ui(filename)