def do_up(self, arg):
        """u(p) [count]
        Move the current frame count (default one) levels up in the
        stack trace (to an older frame).
        """
        if self.curindex == 0:
            self.error('Oldest frame')
            return
        try:
            count = int(arg or 1)
        except ValueError:
            self.error('Invalid frame count (%s)' % arg)
            return
        if count < 0:
            newframe = 0
        else:
            newframe = max(0, self.curindex - count)
        self._select_frame(newframe)
u(p) [count]
        Move the current frame count (default one) levels up in the
        stack trace (to an older frame).