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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 cli(env, identifier):
 """List NAS account credentials."""


    nw_mgr = SoftLayer.NetworkManager(env.client)
    result = nw_mgr.get_nas_credentials(identifier)
    table = formatting.Table(['username', 'password'])
    table.add_row([result.get('username', 'None'),
                   result.get('password', 'None')])
    env.fout(table)