add is_decoder as an attribute to Config class

transformers/modeling_bert.py

@@ -322,7 +322,7 @@ class BertLayer(nn.Module):
     def __init__(self, config):
         super(BertLayer, self).__init__()
         self.self_attention = BertAttention(config)
-        if config.get("is_decoder", False):
+        if getattr(config, "is_decoder", False):
             self.attention = BertAttention(config)
         self.intermediate = BertIntermediate(config)
         self.output = BertOutput(config)
@@ -380,7 +380,7 @@ class BertEncoder(nn.Module):
 class BertDecoder(nn.Module):
     def __init__(self, config):
         super(BertDecoder, self).__init__()
-        config["is_decoder"] = True
+        config.is_decoder = True
         self.output_attentions = config.output_attentions
         self.output_hidden_states = config.output_hidden_states
         self.layers = nn.ModuleList([BertLayer(config) for _ in range(config.num_hidden_layers)])