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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 init(parser = None):
 """ module needs to be initialized by 'init'. Can be called with parser to use a pre-built parser, otherwise a simple default parser is created """


    global p,subparsers
    if parser is None:
        p = argparse.ArgumentParser()
    else:
        p = parser

    arg = p.add_argument

    subparsers = p.add_subparsers()