def _leave_event_hide(self):
        """ Hides the tooltip after some time has passed (assuming the cursor is
            not over the tooltip).
        """
        if (not self._hide_timer.isActive() and
            # If Enter events always came after Leave events, we wouldn't need
            # this check. But on Mac OS, it sometimes happens the other way
            # around when the tooltip is created.
            QtGui.qApp.topLevelAt(QtGui.QCursor.pos()) != self):
            self._hide_timer.start(300, self)
Hides the tooltip after some time has passed (assuming the cursor is
            not over the tooltip).