How to use the greenlet.GREENLET_USE_GC function in greenlet

refcount_before = sys.getrefcount(args)
        g = greenlet.greenlet(
            lambda *args: greenlet.getcurrent().parent.switch(*args))
        for i in range(100):
            g.switch(*args)
        self.assertEqual(sys.getrefcount(args), refcount_before)

    def test_kwarg_refs(self):
        kwargs = {}
        g = greenlet.greenlet(
            lambda **kwargs: greenlet.getcurrent().parent.switch(**kwargs))
        for i in range(100):
            g.switch(**kwargs)
        self.assertEqual(sys.getrefcount(kwargs), 2)

    if greenlet.GREENLET_USE_GC:
        # These only work with greenlet gc support

        def recycle_threads(self):
            # By introducing a thread that does sleep we allow other threads,
            # that have triggered their __block condition, but did not have a
            # chance to deallocate their thread state yet, to finally do so.
            # The way it works is by requring a GIL switch (different thread),
            # which does a GIL release (sleep), which might do a GIL switch
            # to finished threads and allow them to clean up.
            def worker():
                time.sleep(0.001)
            t = threading.Thread(target=worker)
            t.start()
            time.sleep(0.001)
            t.join()

import gc
import sys
import unittest
import weakref

import greenlet


class GCTests(unittest.TestCase):
    def test_dead_circular_ref(self):
        o = weakref.ref(greenlet.greenlet(greenlet.getcurrent).switch())
        gc.collect()
        self.assertTrue(o() is None)
        self.assertFalse(gc.garbage, gc.garbage)

    if greenlet.GREENLET_USE_GC:
        # These only work with greenlet gc support

        def test_circular_greenlet(self):
            class circular_greenlet(greenlet.greenlet):
                pass
            o = circular_greenlet()
            o.self = o
            o = weakref.ref(o)
            gc.collect()
            self.assertTrue(o() is None)
            self.assertFalse(gc.garbage, gc.garbage)

        def test_inactive_ref(self):
            class inactive_greenlet(greenlet.greenlet):
                def __init__(self):
                    greenlet.greenlet.__init__(self, run=self.run)