human
Give me a Python program to print _(\'Hello, world!\') given the following:
Complete the below
def extract(method, fileobj, keywords=DEFAULT_KEYWORDS, comment_tags=(), options=None, strip_comment_tags=False):

    ''''Extract messages from the given file-like object using the specified
    extraction method.
    This function returns a list of tuples of the form:
    ``(lineno, message, comments)``
    The implementation dispatches the actual extraction to plugins, based on the
    value of the ``method`` parameter.
    >>> source = \'\'\'# foo module
    ... def run(argv):
    ...    print _(\'Hello, world!\')
    >>> from StringIO import StringIO
    >>> for message in extract(\'python\', StringIO(source)):
    ...     print message
    (3, u\'Hello, world!\', [])
    :param method: a string specifying the extraction method (.e.g. "python");
    if this is a simple name, the extraction function will be
    looked up by entry point.
if it is an explicit reference
    to a function (of the form ``package.module:funcname`` or
    ``package.module.funcname``), the corresponding function
    will be imported and used
    :param fileobj: the file-like object the messages should be extracted from
    :param keywords: a dictionary mapping keywords (i.e. names of functions
    that should be recognized as translation functions) to
    tuples that specify which of their arguments contain
    localizable strings
    :param comment_tags: a list of translator tags to search for and include
    in the results
    :param options: a dictionary of additional options (optional)
    :param strip_comment_tags: a flag that if set to `True` causes all comment
    tags to be removed from the collected comments.
    :return: the list of extracted messages
    :rtype: `list`
    :raise ValueError: if the extraction method is not registered'
    '''
assistant
#Here is Python program to print _(\'Hello, world!\')
.
    func = None
    if ((':' in method) or ('.' in method)):
        if (':' not in method):
            lastdot = method.rfind('.')
            (module, attrname) = (method[:lastdot], method[(lastdot + 1):])
        else:
            (module, attrname) = method.split(':', 1)
        func = getattr(__import__(module, {}, {}, [attrname]), attrname)
    else:
        try:
            from pkg_resources import working_set
        except ImportError:
            builtin = {'ignore': extract_nothing, 'python': extract_python}
            func = builtin.get(method)
        else:
            for entry_point in working_set.iter_entry_points(GROUP_NAME, method):
                func = entry_point.load(require=True)
                break
    if (func is None):
        raise ValueError(('Unknown    extraction    method    %r' % method))
    results = func(fileobj, keywords.keys(), comment_tags, options=(options or {}))
    for (lineno, funcname, messages, comments) in results:
        if funcname:
            spec = (keywords[funcname] or (1,))
        else:
            spec = (1,)
        if (not isinstance(messages, (list, tuple))):
            messages = [messages]
        if (not messages):
            continue
        msgs = []
        invalid = False
        last_index = len(messages)
        for index in spec:
            if (last_index < index):
                invalid = True
                break
            message = messages[(index - 1)]
            if (message is None):
                invalid = True
                break
            msgs.append(message)
        if invalid:
            continue
        first_msg_index = (spec[0] - 1)
        if (not messages[first_msg_index]):
            where = ('%s:%i' % (((hasattr(fileobj, 'name') and fileobj.name) or '(unknown)'), lineno))
            print >>sys.stderr, (empty_msgid_warning % where)
            continue
        messages = tuple(msgs)
        if (len(messages) == 1):
            messages = messages[0]
        if strip_comment_tags:
           ...