fix ConsinFixmatch bug

ppcls/optimizer/learning_rate.py

@@ -502,6 +502,7 @@ class CosineFixmatch(LRBase):
         self.num_warmup_steps = num_warmup_steps
         self.num_cycles = num_cycles
         self.last_epoch = last_epoch
+        self.by_epoch = by_epoch
 
     def __call__(self):
         def _lr_lambda(current_step):
@@ -517,4 +518,4 @@ class CosineFixmatch(LRBase):
             lr_lambda=_lr_lambda,
             last_epoch=self.last_epoch)
         setattr(learning_rate, "by_epoch", self.by_epoch)
-        return learning_rate
\ No newline at end of file
+        return learning_rate