update parallel_helper (#17691)

test=develop

python/paddle/fluid/dygraph/parallel_helper.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 import os
 from ..layers import collective
-
+from ..framework import Parameter
 __parallel_ctx__clz__ = None
 
 
@@ -39,5 +39,5 @@ def _init_parallel_ctx():
 
 def _broadcast_parameters(parameters):
     for param in parameters:
-        if param.trainable:
+        if isinstance(param, Parameter) and param.trainable:
             collective._broadcast(param, 0, sync_mode=True)