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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 main():
 """This demo shows the main features of the pythondialog Dialog class. """

    try:
        demo()
    except dialog.error, exc_instance:
        sys.stderr.write("Error:\n\n%s\n" % exc_instance.complete_message())
        sys.exit(1)
        
    sys.exit(0)