!583 Check legal value

Merge pull request !583 from fanglei/checklegalvalue

mindspore/nn/optim/optimizer.py

@@ -88,14 +88,12 @@ class Optimizer(Cell):
         if isinstance(weight_decay, int):
             weight_decay = float(weight_decay)
 
-        if not isinstance(weight_decay, float):
-            raise TypeError("weight_decay should be a float number!")
+        validator.check_float_legal_value('weight_decay', weight_decay, None)
 
         if isinstance(loss_scale, int):
             loss_scale = float(loss_scale)
 
-        if not isinstance(loss_scale, float):
-            raise TypeError("loss_scale should be a float number!")
+        validator.check_float_legal_value('loss_scale', loss_scale, None)
 
         if loss_scale <= 0.0:
             raise ValueError("Loss scale should be greater than 0, but got {}".format(loss_scale))