<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_scroll_bar(self):
 """Packs the scrollbar. """

        adj = self.terminal.get_vadjustment()
        scroll = Gtk.VScrollbar(adj)
        scroll.show()
        self.pack_start(scroll, False, False, 0)