fix the problem of BatchNorm config failure at Amp O3 level and some unexpected indent

mindspore/train/amp.py

@@ -127,7 +127,8 @@ def build_train_network(network, optimizer, loss_fn=None, level='O0', **kwargs):
             - O2: Cast network to float16, keep batchnorm and `loss_fn` (if set) run in float32,
               using dynamic loss scale.
             - O3: Cast network to float16, with additional property 'keep_batchnorm_fp32=False'.
-            O2 is recommended on GPU, O3 is recommemded on Ascend.
+
+            O2 is recommended on GPU, O3 is recommended on Ascend.
 
         cast_model_type (:class:`mindspore.dtype`): Supports `mstype.float16` or `mstype.float32`.
             If set to `mstype.float16`, use `float16` mode to train. If set, overwrite the level setting.

mindspore/train/model.py

@@ -59,6 +59,7 @@ class Model:
             - O0: Do not change.
             - O2: Cast network to float16, keep batchnorm run in float32, using dynamic loss scale.
             - O3: Cast network to float16, with additional property 'keep_batchnorm_fp32=False'.
+
             O2 is recommended on GPU, O3 is recommended on Ascend.
 
         loss_scale_manager (Union[None, LossScaleManager]): If None, not scale the loss, or else
@@ -113,7 +114,7 @@ class Model:
         self._build_predict_network()
 
     def _process_amp_args(self, kwargs):
-        if self._amp_level == "O0":
+        if self._amp_level in ["O0", "O3"]:
             self._keep_bn_fp32 = False
         if 'keep_batchnorm_fp32' in kwargs:
             self._keep_bn_fp32 = kwargs['keep_batchnorm_fp32']