src/transformers/models/ibert/modeling_ibert.py/IBertClassificationHead/forward
class IBertClassificationHead:    def forward(self, features, **kwargs):
        hidden_states = features[:, 0, :]  # take <s> token (equiv. to [CLS])
        hidden_states = self.dropout(hidden_states)
        hidden_states = self.dense(hidden_states)
        hidden_states = torch.tanh(hidden_states)
        hidden_states = self.dropout(hidden_states)
        hidden_states = self.out_proj(hidden_states)
        return hidden_states