src/transformers/models/perceiver/modeling_perceiver.py/PerceiverOneHotPreprocessor/forward
class PerceiverOneHotPreprocessor:    def forward(self, inputs: torch.Tensor, pos: Optional[torch.Tensor] = None, network_input_is_1d: bool = True):
        # Add a dummy index dimension.
        inputs = inputs[:, None, :]

        # No position encodings, so the 1st (input) and 3rd (inputs_without_pos)
        # outputs are identical.
        return inputs, None, inputs