How to use the greenlet.greenlet.GreenletExit function in greenlet

def test_dealloc(self):
        seen = []
        g1 = greenlet(fmain)
        g2 = greenlet(fmain)
        g1.switch(seen)
        g2.switch(seen)
        self.assertEqual(seen, [])
        del g1
        gc.collect()
        self.assertEqual(seen, [greenlet.GreenletExit])
        del g2
        gc.collect()
        self.assertEqual(seen, [greenlet.GreenletExit, greenlet.GreenletExit])

def test_kill(self):
        def f():
            switch("ok")
            switch("fail")
        g = greenlet(f)
        res = g.switch()
        self.assertEqual(res, "ok")
        res = g.throw()
        self.assertTrue(isinstance(res, greenlet.GreenletExit))
        self.assertTrue(g.dead)
        res = g.throw()    # immediately eaten by the already-dead greenlet
        self.assertTrue(isinstance(res, greenlet.GreenletExit))

if self.delta_count > self.max_delta_count:
                    self._finalize()
                    self.events['run_end'](self)
                    self._finished = True
                    raise Exception("Maximum number of delta cycles reached: {0}".format(self.max_delta_count))
                
#                 print('-----------------------------------------')
                
            self.events['timestep_end'](self.time, self)
            
            # All events have settled, let's advance time
            if not self._advance_time():
                self._finalize()
                self.events['run_end'](self)
                self._finished = True
                raise greenlet.GreenletExit 

raise greenlet.GreenletExit
                    raise Exception("Maximum number of delta cycles reached: {0}".format(self.max_delta_count))
                
                if not (self._ready_pool or self.trig_pool):
                    self.events['delta_settled'](self)
                
#                 print('-----------------------------------------')
                 
            self.events['timestep_end'](self.time, self)
             
            # All events have settled, let's advance time
            if not self._advance_time():
                self._finalize()
                self.events['run_end'](self)
                self._finished = True
                raise greenlet.GreenletExit