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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 get_csv(filename):
 """ Return a csv representation of the exif get a filename and returns a unicode string with a CSV format Arguments: filename {string} -- your filename Returns: [unicode] -- unicode string """

    check_if_this_file_exist(filename)

    #Process this function
    filename = os.path.abspath(filename)
    s = command_line(['exiftool', '-G', '-csv', '-sort', filename])
    if s:
        #convert bytes to string
        s = s.decode('utf-8')
        return s
    else:
        return 0