human
Complete this python program:
def babel_extract(fileobj, keywords, comment_tags, options):
assistant
#Here is the Python code you requested.

    """Babel extraction method for Jinja templates.
    .. versionchanged:: 2.3
    Basic support for translation comments was added.  If `comment_tags`
    is now set to a list of keywords for extraction, the extractor will
    try to find the best preceeding comment that begins with one of the
    keywords.  For best results, make sure to not have more than one
    gettext call in one line of code and the matching comment in the
    same line or the line before.
    .. versionchanged:: 2.5.1
    The `newstyle_gettext` flag can be set to `True` to enable newstyle
    gettext calls.
    :param fileobj: the file-like object the messages should be extracted from
    :param keywords: a list of keywords (i.e. function names) that should be
    recognized as translation functions
    :param comment_tags: a list of translator tags to search for and include
    in the results.
    :param options: a dictionary of additional options (optional)
    :return: an iterator over ``(lineno, funcname, message, comments)`` tuples.
    (comments will be empty currently)
    """
    extensions = set()
    for extension in options.get('extensions', '').split(','):
        extension = extension.strip()
        if (not extension):
            continue
        extensions.add(import_string(extension))
    if (InternationalizationExtension not in extensions):
        extensions.add(InternationalizationExtension)
    def getbool(options, key, default=False):
        (options.get(key, str(default)).lower() in ('1', 'on', 'yes', 'true'))
    environment = Environment(options.get('block_start_string', BLOCK_START_STRING), options.get('block_end_string', BLOCK_END_STRING), options.get('variable_start_string', VARIABLE_START_STRING), options.get('variable_end_string', VARIABLE_END_STRING), options.get('comment_start_string', COMMENT_START_STRING), options.get('comment_end_string', COMMENT_END_STRING), (options.get('line_statement_prefix') or LINE_STATEMENT_PREFIX), (options.get('line_comment_prefix') or LINE_COMMENT_PREFIX), getbool(options, 'trim_blocks', TRIM_BLOCKS), NEWLINE_SEQUENCE, frozenset(extensions), cache_size=0, auto_reload=False)
    if getbool(options, 'newstyle_gettext'):
        environment.newstyle_gettext = True
    source = fileobj.read().decode(options.get('encoding', 'utf-8'))
    try:
        node = environment.parse(source)
        tokens = list(environment.lex(environment.preprocess(source)))
    except TemplateSyntaxError as e:
        return
    finder = _CommentFinder(tokens, comment_tags)
    for (lineno, func, message) in extract_from_ast(node, keywords):
        (yield (lineno, func, message, finder.find_comments(lineno)))