def set_is_pallets_theme(app):
    """Set the ``is_pallets_theme`` config to ``True`` if the current
    theme is a decedent of the ``pocoo`` theme.
    """
    if app.config.is_pallets_theme is not None:
        return
    theme = getattr(app.builder, 'theme', None)
    while theme is not None:
        if theme.name == 'pocoo':
            app.config.is_pallets_theme = True
            break
        theme = theme.base
    else:
        app.config.is_pallets_theme = False
