When soing guidance loss, make CFG zero an optional target instead of a forced one.

toolkit/config_modules.py

@@ -541,6 +541,7 @@ class TrainConfig:
         # contrastive loss
         self.do_guidance_loss = kwargs.get('do_guidance_loss', False)
         self.guidance_loss_target: Union[int, List[int, int]] = kwargs.get('guidance_loss_target', 3.0)
+        self.do_guidance_loss_cfg_zero: bool = kwargs.get('do_guidance_loss_cfg_zero', False)
         self.unconditional_prompt: str = kwargs.get('unconditional_prompt', '')
         if isinstance(self.guidance_loss_target, tuple):
             self.guidance_loss_target = list(self.guidance_loss_target)