How to use the autopep8.detect_encoding function in autopep8

def readlines(filename):
    """Return contents of file as a list of lines."""
    with autopep8.open_with_encoding(
            filename,
            encoding=autopep8.detect_encoding(filename)) as f:
        return f.readlines()

"""
    got = autopep8.fix_file(
        input_filename,
        options=autopep8.parse_args([''] + aggressive * ['--aggressive']))

    try:
        with autopep8.open_with_encoding(expected_filename) as expected_file:
            expected = expected_file.read()
    except IOError:
        expected = None

    if expected == got:
        return True
    else:
        got_filename = expected_filename + '.err'
        encoding = autopep8.detect_encoding(input_filename)

        with autopep8.open_with_encoding(got_filename,
                                         encoding=encoding,
                                         mode='w') as got_file:
            got_file.write(got)

        print(
            '{begin}{got} does not match expected {expected}{end}'.format(
                begin=RED,
                got=got_filename,
                expected=expected_filename,
                end=END),
            file=sys.stdout)

        return False

def format_file(filename, args, standard_out):
    """Run format_code() on a file.

    Return True if the new formatting differs from the original.

    """
    encoding = autopep8.detect_encoding(filename)
    with autopep8.open_with_encoding(filename,
                                     encoding=encoding) as input_file:
        source = input_file.read()

    if not source:
        return False

    formatted_source = format_code(
        source,
        aggressive=args.aggressive,
        apply_config=args.config,
        filename=filename,
        remove_all_unused_imports=args.remove_all_unused_imports,
        remove_unused_variables=args.remove_unused_variables)

    if source != formatted_source: