fix bugs

fairseq/models/dense_relative_transformer.py

@@ -474,7 +474,7 @@ def base_architecture(args):
     args.decoder_history_type = getattr(args, 'decoder_history_type', 'dense')
     args.encoder_integration_type = getattr(args, 'encoder_integration_type', 'avg')
     args.decoder_integration_type = getattr(args, 'decoder_integration_type', 'avg')
-    args.max_relative_length = 20 = getattr(args, 'max_relative_length', 20)
+    args.max_relative_length = getattr(args, 'max_relative_length', 20)
 
 
 @register_model_architecture('dense_relative_transformer', 'dense_relative_transformer_wmt_en_de')