def METHOD_NAME():
    from .form import SingleTag
    add_form = SingleTag(request.form)
    if not add_form.validate():
        for widget, l in add_form.errors.items():
            flash(','.join(l), 'error')
        return redirect(url_for('tags.tags_overview_page'))
    title = request.form.get('name').strip()
    if datastore.tag_exists_by_name(title):
        flash(f'The tag "{title}" already exists', "error")
        return redirect(url_for('tags.tags_overview_page'))
    datastore.add_tag(title)
    flash("Tag added")
    return redirect(url_for('tags.tags_overview_page'))