How to use the invenio.base.i18n.gettext_set_language function in invenio

def tmpl_draw_titlebar(self, ln, title, guideurl, extraname="", extraurl=""):
        """Draws an html title bar
          - 'title' *string* - The name of the titlebar
          - 'guideurl' *string* - The relative url of the guide relative to this section
          - 'extraname' *string* - The name of an extra function
          - 'extraurl' *string* - The relative url to an extra function
          """
        _ = gettext_set_language(ln)
        guidetitle = _("See Guide")

        titlebar = """ <table class="table"><tbody><tr><th>"""
        titlebar += """%s<small>[<a href="%s/%s" title="%s">?</a>]</small>""" % (title, guidetitle, CFG_SITE_URL, guideurl)
        if extraname and extraurl:
            titlebar += self.tmpl_button_link(extraname, CFG_SITE_URL + extraurl)
        titlebar += """</th></tr></tbody></table>"""
        return titlebar

        @param cmtid: id of comment (int)
        @param category: category (see webbasket_config) (str)
        @param topic: nb of topic currently displayed (int)
        @param group: id of group baskets currently displayed (int)
        @param ln: language"""

        argd = wash_urlargd(form, {'category': (str, cfg['CFG_WEBBASKET_CATEGORIES']['PRIVATE']),
                                   'topic': (str, ""),
                                   'group': (int, 0),
                                   'bskid': (int, 0),
                                   'recid': (int, 0),
                                   'cmtid': (int, 0),
                                   'of'   : (str, ''),
                                   'ln': (str, CFG_SITE_LANG)})

        _ = gettext_set_language(argd['ln'])

        uid = getUid(req)
        if uid == -1 or CFG_ACCESS_CONTROL_LEVEL_SITE >= 1:
            return page_not_authorized(req, "../yourbaskets/delete_note",
                                       navmenuid = 'yourbaskets')

        if isGuestUser(uid):
            return redirect_to_url(req, "%s/youraccount/delete_note%s" % (
                CFG_SITE_SECURE_URL,
                    make_canonical_urlargd({
                'referer' : "%s/yourbaskets/display%s" % (
                    CFG_SITE_SECURE_URL,
                    make_canonical_urlargd(argd, {})),
                "ln" : argd['ln']}, {})))

        user_info = collect_user_info(req)

def external_collection_overview(self, lang=CFG_SITE_LANG, engine_list=()):
        """Prints results overview box with links to particular collections below.
        lang: The language to display
        engine_list: The external engines to be used"""

        if len(engine_list) < 1:
            return ""

        _ = gettext_set_language(lang)

        out = """
  <table class="externalcollectionsresultsbox">
    <thead>
      <tr>
        <th class="externalcollectionsresultsboxheader"><strong>%s</strong></th>
      </tr>
    </thead>
      <tbody>
        <tr>
          <td class="externalcollectionsresultsboxbody"> """ % _("External collections results overview:")

        for engine in engine_list:
            internal_name = get_link_name(engine.name)
            name = _(engine.name)
            out += """<strong><a href="#%(internal_name)s">%(name)s</a></strong><br>""" % locals()</td></tr></tbody></table>

def perform_request_groups_display(uid, infos=[], warnings = [], \
        ln=CFG_SITE_LANG):
    """Display all the groups the user belongs to.
    @param uid:   user id
    @param info: info about last user action
    @param ln: language
    @return: body with warnings
    """
    _ = gettext_set_language(ln)
    body = ""

    body_admin = display_admin_groups(uid, ln)
    body_member = display_member_groups(uid, ln)
    body_external = display_external_groups(uid, ln)

    body = websession_templates.tmpl_display_all_groups(infos=infos,
        admin_group_html=body_admin,
        member_group_html=body_member,
        external_group_html=body_external,
        warnings=warnings,
        ln=ln)
    return body

def answer(self, req, user_info, of, cc, colls_to_search, p, f, search_units, ln):
        """
        Answer question given by context.

        Return (relevance, html_string) where relevance is integer
        from 0 to 100 indicating how relevant to the question the
        answer is (see C{CFG_WEBSEARCH_SERVICE_MAX_SERVICE_ANSWER_RELEVANCE} for details) ,
        and html_string being a formatted answer.
        """
        from invenio.legacy.search_engine import \
             get_permitted_restricted_collections, \
             get_coll_i18nname, \
             collection_i18nname_cache, \
             collection_restricted_p
        _ = gettext_set_language(ln)
        # stem search units. remove those with field
        # TODO: search in hosted collection names too
        # TODO: ignore unattached trees
        # TODO: use synonyms
        if f or (CFG_WEBSEARCH_COLLECTION_NAMES_SEARCH < 0) or \
               (CFG_WEBSEARCH_COLLECTION_NAMES_SEARCH == 0 and cc != CFG_SITE_NAME):
            return (0, '')

        words = [stem(unit[1], ln) for unit in search_units if unit[2] in ('', 'collection')] # Stemming

        if not words:
            return (0, '')

        permitted_restricted_collections = get_permitted_restricted_collections(user_info)
        cache = self.get_data_cache()

def not_authorized(self, req, form):
        """Displays page telling the user that
        he is not authorised to access the resource"""
        argd = wash_urlargd(form, {})

        # load the right message language
        language = argd["ln"]
        _ = gettext_set_language(language)

        text = _("You are not authorised to access this resource.")
        return page_not_authorized(req = req, ln = language, text = text)

def get_users_by_status(grpID, status, ln=CFG_SITE_LANG):
    """Get the list of users with the given status.
    @return: ((id, nickname),) nickname= user # uid if
    the user has no nickname
    """
    _ = gettext_set_language(ln)
    res = run_sql("""SELECT ug.id_user, u.nickname
                       FROM user_usergroup ug, "user" u
                      WHERE ug.id_usergroup = %s
                        AND ug.id_user=u.id
                        AND user_status = %s""",
                  (grpID, status))
    users = []
    if res:
        for (mid, nickname) in res:
            nn = nickname
            if not nickname:
                nn = _("user") + "#%i" % mid
            users.append((mid, nn))
    return tuple(users)

action='',
                           ln=CFG_SITE_LANG):
    """
    Interface to feature a record

    Used to list, add and remove featured records of the journal.

    Parameters:
        journal_name  -  the journal for which the article is featured
               recid  -  the record affected by 'action'
             img_url  -  the URL to image displayed with given record
                         (only when action == 'add')
              action  -  One of ['', 'add', 'askremove', _('Remove'), _('Cancel')]
                  ln  -  language
    """
    _ = gettext_set_language(ln)

    if action == 'add':
        result = add_featured_record(journal_name, recid, img_url)
        if result == 0:
            msg ='''<span style="color:#0f0">Successfully featured
            <a href="%(CFG_SITE_URL)s/%(CFG_SITE_RECORD)s/%(recid)s">record %(recid)s</a>.
        Go to the <a href="%(CFG_SITE_URL)s/journal/%(name)s">%(name)s journal</a> to
        see the result.</span>''' % {'CFG_SITE_URL': CFG_SITE_URL,
                                  'CFG_SITE_RECORD': CFG_SITE_RECORD,
                                  'name': journal_name,
                                  'recid': recid}
        elif result == 1:
            msg = '''<span style="color:#f00"><a href="%(CFG_SITE_URL)s/%(CFG_SITE_RECORD)s/%(recid)s">record %(recid)s</a> is already featured. Choose another one or remove it first.</span>''' % \
                  {'CFG_SITE_URL': CFG_SITE_URL,
                   'CFG_SITE_RECORD': CFG_SITE_RECORD,
                   'recid': recid}

def perform_request_edit_group(uid,
        grpID,
        warnings=[],
        ln=CFG_SITE_LANG):
    """Return html for group editing.
    @param uid: user ID
    @param grpID: ID of the group
    @param warnings: warnings
    @param ln: language
    @return: body with warnings
    """
    body = ""
    _ = gettext_set_language(ln)
    user_status = db.get_user_status(uid, grpID)
    if not len(user_status):
        try:
            raise InvenioWebSessionError(_('Sorry, there was an error with the database.'))
        except InvenioWebSessionError as exc:
            register_exception()
            body = websession_templates.tmpl_error(exc.message, ln)
            return body
    elif user_status[0][0] != CFG_WEBSESSION_USERGROUP_STATUS['ADMIN']:
        try:
            raise InvenioWebSessionError(_('Sorry, you do not have sufficient rights on this group.'))
        except InvenioWebSessionError as exc:
            register_exception()
            body = websession_templates.tmpl_error(exc.message, ln)
            return body
    group_infos = db.get_group_infos(grpID)[0]

def perform_request_harvest_record(oai_src_id=None, ln=CFG_SITE_LANG, record_id=None, uid=None, confirm=0, enable_reporting=True):
    """ Request for harvesting a new record """
    _ = gettext_set_language(ln)
    if oai_src_id is None:
        return oaiharvest_templates.tmpl_print_warning(ln, _("No OAI source ID selected."))
    result = ""
    guideurl = "help/admin/oaiharvest-admin-guide"
    result += oaiharvest_templates.tmpl_output_menu(ln, oai_src_id, guideurl)
    result += oaiharvest_templates.tmpl_draw_titlebar(ln=ln,
                                                      title=_(
                                                          "Record OAI IDs ( as recognized by the data source )"),
                                                      guideurl=guideurl)
    record_str = ""
    if record_id:
        record_str = str(record_id)

    # We enable reporting by default, unless user specifies otherwise.
    if confirm in (1, "1") and not enable_reporting:
        enable_reporting = False