docs: 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 = QtCore.QRect(0, top, self.sizeHint().width(),
                              self.sizeHint().height())
          if self._native:
              if os.environ['QT_API'].lower() not in PYQT5_API:
                  opt = QtGui.QStyleOptionViewItemV2()
              else:
                  opt = QtWidgets.QStyleOptionViewItem()
              opt.rect = rect
              opt.state = (QtWidgets.QStyle.State_Active |
                           QtWidgets.QStyle.State_Item |
                           QtWidgets.QStyle.State_Children)
              if not collapsed:
                  opt.state |= QtWidgets.QStyle.State_Open
              if mouse_over:
                  opt.state |= (QtWidgets.QStyle.State_MouseOver |
                                QtWidgets.QStyle.State_Enabled |
                                QtWidgets.QStyle.State_Selected)
                  opt.palette.setBrush(QtGui.QPalette.Window,
                                       self.palette().highlight())
              opt.rect.translate(-2, 0)
              self.style().drawPrimitive(QtWidgets.QStyle.PE_IndicatorBranch,
                                         opt, painter, self)
          else:
              index = 0
              if not collapsed:
                  index = 2
              if mouse_over:
                  index += 1
              QtGui.QIcon(self._custom_indicators[index]).paint(painter, rect)