python2 assert

Author: Yang Yang

python/paddle/v2/fluid/framework.py

@@ -434,8 +434,9 @@ def find_name(var_list, name):
                             % (in_proto.name, len(in_args)))
                     in_arg_names = []
                     for arg in in_args:
-                        assert (isinstance(arg, Variable),
-                                "Input of an operator must be variables.")
+                        assert isinstance(
+                            arg,
+                            Variable), "Input of an operator must be variables."
                         in_arg_names.append(arg.name)
                     self.desc.set_input(in_proto.name, in_arg_names)
                 else: