Set the garbage collection debugging flags.
flags
An integer that can have the following bits turned on:
DEBUG_STATS - Print statistics during collection.
DEBUG_COLLECTABLE - Print collectable objects found.
DEBUG_UNCOLLECTABLE - Print unreachable but uncollectable objects
found.
DEBUG_SAVEALL - Save objects to gc.garbage rather than freeing them.
DEBUG_LEAK - Debug leaking programs (everything but STATS).
Debugging information is written to sys.stderr.