text: Title: Save cfg.TRAIN.START_EPOCH to state dict
  Body: Well #77 didn't work for me while resuming from checkpoint_18.pth. The problem is when we resume, the model and optimizer passed in the restore_from function are suitable for epoch less than 10 (till backbone is not training) because the cfg.TRAIN.START_EPOCH is 0 (passed in build_opt_lr function just before restore_from) initially so this mismatches the optimizer after backbone start training. So to resume my training , I pass the cfg.TRAIN.START_EPOCH as 19 and when build_opt_lr function receives epoch greater than 10 (i.e Backbone training starts) it produces the model and optimizer suitable for resuming. And i can resume my training.
  
  _Originally posted by @PhenomenalOnee in https://github.com/STVIR/pysot/issues/92#issuecomment-651571350_