examples/research_projects/lxmert/modeling_frcnn.py/ResNet/forward
class ResNet:    def forward(self, x):
        outputs = {}
        x = self.stem(x)
        if "stem" in self._out_features:
            outputs["stem"] = x
        for stage, name in self.stages_and_names:
            x = stage(x)
            if name in self._out_features:
                outputs[name] = x
        if self.num_classes is not None:
            x = self.avgpool(x)
            x = self.linear(x)
            if "linear" in self._out_features:
                outputs["linear"] = x
        return outputs