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

    @safe_translation
    def _make_mail(locale, user, watch):
        context_vars['user'] = user
        context_vars['watch'] = watch[0]
        context_vars['watches'] = watch
        mail = make_mail(subject.format(**context_vars), text_template, html_template, context_vars, from_email, user.email, **extra_kwargs)
        return mail
    for (u, w) in users_and_watches:
        if hasattr(u, 'profile'):
            locale = u.profile.locale
        else:
            locale = default_locale
        (yield _make_mail(locale, u, w))

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

def emails_with_users_and_watches(subject, text_template, html_template, context_vars, users_and_watches, from_email=settings.TIDINGS_FROM_ADDRESS, default_locale=settings.WIKI_DEFAULT_LANGUAGE, **extra_kwargs):