update double head model

pytorch_pretrained_bert/modeling_openai.py

@@ -371,7 +371,7 @@ class OpenAIGPTMultipleChoiceHead(nn.Module):
     def forward(self, hidden_states, mc_token_ids):
         # Classification logits
         # hidden_state (bsz, num_choices, seq_length, hidden_size)
-        # mc_token_ids (bsz, num_choices, 1)
+        # mc_token_ids (bsz, num_choices)
         mc_token_ids = mc_token_ids.unsqueeze(-1).unsqueeze(-1).expand(-1, -1, -1, hidden_states.size(-1))
         # (bsz, num_choices, 1, hidden_size)
         multiple_choice_h = hidden_states.gather(2, mc_token_ids).squeeze(2)