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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 yank_last_arg(event):
 """ Like `yank_nth_arg`, but if no argument has been given, yank the last word of each line. """

    n = (event.arg if event.arg_present else None)
    event.current_buffer.yank_last_arg(n)