code: def subcmd_prepare_parser(subcmd):
      
      subcmd.add_argument(
          '--provider',
          action='store',
          dest='provider',
          help=u'Targeted cluster type',
          choices=['openshift', 'kubernetes'],
          default='openshift'
      )
  
      subcmd.add_argument(
          '--dockerfile',
          '-f',
          action='store',
          dest='dockerfile',
          help=u'Name of Dockerfile to build with'
      )
  
      return
docs: prepare subcommand