Which variable in the following code is used to display a message when a user accesses the argparse module help?

import arparse

argparse$\_$help $=$ 'help'

parser $=$ argparse.ArgumentParser$($description$=$argparse$\_$help$)$

parser.add$\_$argument$("-$R$","$arg$\_$help", help$="$ Enter router name"$)$

arg$\_$help $=$ parser.parse$\_$args$()$