Override Qt method.

        Paint breakpoints icons.

def paintEvent(self, event):
        """Override Qt method.

        Paint breakpoints icons.
        """
        super(DebuggerPanel, self).paintEvent(event)
        painter = QPainter(self)
        painter.fillRect(event.rect(), self.editor.sideareas_color)

        for top, line_number, block in self.editor.visible_blocks:
            if self.line_number_hint == line_number:
                self._draw_breakpoint_icon(top, painter, 'transparent')
            if self._current_line_arrow == line_number and not self.stop:
                self._draw_breakpoint_icon(top, painter, 'arrow')

            data = block.userData()
            if data is None or not data.breakpoint:
                continue

            if data.breakpoint_condition is None:
                self._draw_breakpoint_icon(top, painter, 'breakpoint')
            else:
                self._draw_breakpoint_icon(top, painter, 'condition')