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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 command_line():
    '''
    Parses users command line arguments and returns the namespace
    containing parsed values.
    '''
    description = 'Kan helps you find the book'
    version     = ' '.join([__version__, __release__])
    parser      = ArgumentParser(prog='kan', description=description)

    subparser   = parser.add_subparsers(help='Search by')

    by_title    = subparser.add_parser('title', help='Book title',)
    by_title.add_argument('title', help='Book name')

    by_isbn     = subparser.add_parser('isbn', help='ISBN code')
    by_isbn.add_argument('code', help='Valid ISBN code')

    by_author   = subparser.add_parser('author', help='Book author')
    by_author.add_argument('author', help='Authors name')
    by_author.add_argument('--recent', help='Search by most recent', action='store_true')
    by_author.add_argument('--top', help='Search by best selling', action='store_true')

    # Main Parser
    parser.add_argument(
        '-v', '--version', action='version',
        version="%s v%s" % ('kan', version),
    )
    parser.add_argument(
        '--title',
        help='Title of the book',
        metavar='name',
    )
    parser.add_argument(
        '--author',
        default=None,
        metavar='name',
        help='Name of the author',
    )
    parser.add_argument(
        '--subject',
        type=str,
        help='Specify subject matter by category',
        metavar='topic',
    )
    parser.add_argument(
        '--max',
        type=int,
        metavar='n',
        default=3,
        choices=range(41),
        help='Maximum results to get per query: default=3, max=40',
    )
    parser.add_argument(
        '--language',
        type=str,
        metavar='code',
        default='',
        help='Restrict the search results to those with a certain language code',
    )
    parser.add_argument(
        '--verbose',
        action='store_true',
        help='Print out debug information',
    )

    return parser.parse_args()