src/transformers/models/lxmert/modeling_lxmert.py/LxmertForQuestionAnswering/get_qa_logit_layer
class LxmertForQuestionAnswering:    def get_qa_logit_layer(self) -> nn.Module:
        """
        Returns the linear layer that produces question answering logits

        Returns:
            `nn.Module`: A torch module mapping the question answering prediction hidden states. `None`: A NoneType
            object if Lxmert does not have the visual answering head.
        """

        if hasattr(self, "answer_head"):
            return self.answer_head.logit_fc[-1]