Fix arg do_model_average in param_attr (#19376)

* Fix arg do_model_average in param_attr

test=develop

* Update api spec

test=develop

paddle/fluid/API.spec

@@ -1005,8 +1005,8 @@ paddle.fluid.CUDAPlace ('paddle.fluid.core_avx.CUDAPlace', ('document', '6a6cd8e
 paddle.fluid.CUDAPlace.__init__ __init__(self: paddle.fluid.core_avx.CUDAPlace, arg0: int) -> None
 paddle.fluid.CUDAPinnedPlace ('paddle.fluid.core_avx.CUDAPinnedPlace', ('document', 'afd58ea5d390b5ea06ca70291a266d45'))
 paddle.fluid.CUDAPinnedPlace.__init__ __init__(self: paddle.fluid.core_avx.CUDAPinnedPlace) -> None
-paddle.fluid.ParamAttr ('paddle.fluid.param_attr.ParamAttr', ('document', 'fa47fa251f727c4a4f638d61e3c7c141'))
-paddle.fluid.ParamAttr.__init__ (ArgSpec(args=['self', 'name', 'initializer', 'learning_rate', 'regularizer', 'trainable', 'gradient_clip', 'do_model_average'], varargs=None, keywords=None, defaults=(None, None, 1.0, None, True, None, False)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
+paddle.fluid.ParamAttr ('paddle.fluid.param_attr.ParamAttr', ('document', 'cd667b4ee96d7d6fca40aa722d67d744'))
+paddle.fluid.ParamAttr.__init__ (ArgSpec(args=['self', 'name', 'initializer', 'learning_rate', 'regularizer', 'trainable', 'gradient_clip', 'do_model_average'], varargs=None, keywords=None, defaults=(None, None, 1.0, None, True, None, True)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
 paddle.fluid.WeightNormParamAttr ('paddle.fluid.param_attr.WeightNormParamAttr', ('document', 'b5ae1698ea72d5a9428000b916a67379'))
 paddle.fluid.WeightNormParamAttr.__init__ (ArgSpec(args=['self', 'dim', 'name', 'initializer', 'learning_rate', 'regularizer', 'trainable', 'gradient_clip', 'do_model_average'], varargs=None, keywords=None, defaults=(None, None, None, 1.0, None, True, None, False)), ('document', '6adf97f83acf6453d4a6a4b1070f3754'))
 paddle.fluid.DataFeeder ('paddle.fluid.data_feeder.DataFeeder', ('document', 'd9e64be617bd5f49dbb08ac2bc8665e6'))

python/paddle/fluid/param_attr.py

@@ -42,8 +42,8 @@ class ParamAttr(object):
         trainable(bool): Whether this parameter is trainable. Default True.
         gradient_clip(BaseGradientClipAttr): The method to clip this parameter's
             gradient. Default None.
-        do_model_average(bool): Whether this parameter should do model average.
-            Default False.
+        do_model_average(bool): Whether this parameter should do model average 
+            when model average is enabled. Default True.
 
     Examples:
         .. code-block:: python
@@ -65,14 +65,14 @@ class ParamAttr(object):
                  regularizer=None,
                  trainable=True,
                  gradient_clip=None,
-                 do_model_average=False):
+                 do_model_average=True):
         self.name = name
         self.initializer = initializer
         self.learning_rate = learning_rate
         self.regularizer = regularizer
         self.trainable = trainable
         self.gradient_clip = gradient_clip
-        self.model_average = do_model_average
+        self.do_model_average = do_model_average
 
     def _set_default_initializer(self, initializer):
         """
@@ -170,7 +170,7 @@ class ParamAttr(object):
             'regularizer': self.regularizer,
             'trainable': self.trainable,
             'gradient_clip_attr': self.gradient_clip,
-            'model_average': self.model_average
+            'do_model_average': self.do_model_average
         }
         if with_initializer:
             kwargs['initializer'] = self.initializer