Draw the fold indicator/trigger (arrow).

        :param top: Top position
        :param mouse_over: Whether the mouse is over the indicator
        :param collapsed: Whether the trigger is collapsed or not.
        :param painter: QPainter

def _draw_fold_indicator(self, top, mouse_over, collapsed, painter):
        """
        Draw the fold indicator/trigger (arrow).

        :param top: Top position
        :param mouse_over: Whether the mouse is over the indicator
        :param collapsed: Whether the trigger is collapsed or not.
        :param painter: QPainter
        """
        rect = QRect(0, top, self.sizeHint().width(),
                            self.sizeHint().height())
        if self._native_icons:
            opt = QStyleOptionViewItem()

            opt.rect = rect
            opt.state = (QStyle.State_Active |
                         QStyle.State_Item |
                         QStyle.State_Children)
            if not collapsed:
                opt.state |= QStyle.State_Open
            if mouse_over:
                opt.state |= (QStyle.State_MouseOver |
                              QStyle.State_Enabled |
                              QStyle.State_Selected)
                opt.palette.setBrush(QPalette.Window,
                                     self.palette().highlight())
            opt.rect.translate(-2, 0)
            self.style().drawPrimitive(QStyle.PE_IndicatorBranch,
                                       opt, painter, self)
        else:
            index = 0
            if not collapsed:
                index = 2
            if mouse_over:
                index += 1
            ima.icon(self._indicators_icons[index]).paint(painter, rect)