src/transformers/models/bit/modeling_bit.py/BitPreActivationBottleneckLayer/forward
class BitPreActivationBottleneckLayer:    def forward(self, hidden_states):
        hidden_states_preact = self.norm1(hidden_states)

        # shortcut branch
        shortcut = hidden_states
        if self.downsample is not None:
            shortcut = self.downsample(hidden_states_preact)

        # residual branch
        hidden_states = self.conv1(hidden_states_preact)
        hidden_states = self.conv2(self.norm2(hidden_states))
        hidden_states = self.conv3(self.norm3(hidden_states))
        hidden_states = self.drop_path(hidden_states)
        return hidden_states + shortcut