human
Here's a good function header given the following:
I wrote the below code

    catalog = Catalog(locale=locale, domain=domain)
    counter = [0]
    offset = [0]
    messages = []
    translations = []
    locations = []
    flags = []
    user_comments = []
    auto_comments = []
    obsolete = [False]
    in_msgid = [False]
    in_msgstr = [False]
    def _add_message():
        translations.sort()
        if (len(messages) > 1):
            msgid = tuple([denormalize(m) for m in messages])
        else:
            msgid = denormalize(messages[0])
        if isinstance(msgid, (list, tuple)):
            string = []
            for idx in range(catalog.num_plurals):
                try:
                    string.append(translations[idx])
                except IndexError:
                    string.append((idx, ''))
            string = tuple([denormalize(t[1]) for t in string])
        else:
            string = denormalize(translations[0][1])
        message = Message(msgid, string, list(locations), set(flags), auto_comments, user_comments, lineno=(offset[0] + 1))
        if obsolete[0]:
            if (not ignore_obsolete):
                catalog.obsolete[msgid] = message
        else:
            catalog[msgid] = message
        del messages[:]
        del translations[:]
        del locations[:]
        del flags[:]
        del auto_comments[:]
        del user_comments[:]
        obsolete[0] = False
        counter[0] += 1
    def _process_message_line(lineno, line):
        if line.startswith('msgid_plural'):
            in_msgid[0] = True
            msg = line[12:].lstrip()
            messages.append(msg)
        elif line.startswith('msgid'):
            in_msgid[0] = True
            offset[0] = lineno
            txt = line[5:].lstrip()
            if messages:
                _add_message()
            messages.append(txt)
        elif line.startswith('msgstr'):
            in_msgid[0] = False
            in_msgstr[0] = True
            msg = line[6:].lstrip()
            if msg.startswith('['):
                (idx, msg) = msg[1:].split(']', 1)
               ...

What's a good function header?
assistant
#Here's a good function header.

def read_po(fileobj, locale=None, domain=None, ignore_obsolete=False):