code: def cli(env, identifier):
      
  
      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)
docs: List NAS account credentials.