examples/research_projects/visual_bert/modeling_frcnn.py/BasicStem/forward
class BasicStem:    def forward(self, x):
        x = self.conv1(x)
        x = nn.functional.relu_(x)
        if self.caffe_maxpool:
            x = nn.functional.max_pool2d(x, kernel_size=3, stride=2, padding=0, ceil_mode=True)
        else:
            x = nn.functional.max_pool2d(x, kernel_size=3, stride=2, padding=1)
        return x