hi ,

useage instructions and test_net.py code are misleading:
cfg.merge_from_file(args.config_file)
cfg.merge_from_list(args.opts)
cfg.freeze()

in practice , code in maskrcnn_bechmark/utils/checkpoint.py , loads the last existing checkpoint if present:
def load(self, f=None):
if self.has_checkpoint():
# override argument with existing checkpoint
f = self.get_checkpoint_file()
if not f:
# no checkpoint could be found
self.logger.info("No checkpoint found. Initializing model from scratch")
return {}
self.logger.info("Loading checkpoint from {}".format(f))

:-)
Omer.