import gc
import sys
import weakref

class A: pass
class B: pass

gc.disable()
gc.collect()

gc.set_debug(gc.DEBUG_STATS | gc.DEBUG_LEAK)

a = A()
weakref.finalize(a, print, 'finalize: a', file=sys.stderr).atexit = False

b = B()
b.a = a
b.b = b
weakref.finalize(b, print, 'finalize: b', a, file=sys.stderr).atexit = False

del a
del b

for _ in range(10): gc.collect()

gc.set_debug(0)