import os from typing import Any, Optional, Tuple, Union import torch import transformers from torch.nn import CrossEntropyLoss from transformers import PreTrainedTokenizerFast, VisionEncoderDecoderModel from transformers.configuration_utils import PretrainedConfig from transformers.modeling_outputs import BaseModelOutput, Seq2SeqLMOutput from transformers.modeling_utils import PreTrainedModel from transformers.models.vision_encoder_decoder.configuration_vision_encoder_decoder import \ VisionEncoderDecoderConfig from transformers.utils import logging logger = logging.get_logger(__name__) class CvtWithProjectionHeadConfig(transformers.CvtConfig): def __init__(self, projection_size: int = None, **kwargs: Any) -> None: super().__init__(**kwargs) self.projection_size = projection_size class ModelOutputWithProjectionEmbedding(transformers.modeling_outputs.ModelOutput): last_hidden_state: torch.FloatTensor attention_mask: torch.FloatTensor class CvtProjectionHead(torch.nn.Module): def __init__(self, config) -> None: super().__init__() # https://github.com/huggingface/transformers/blob/68287689f2f0d8b7063c400230b3766987abf18d/src/transformers/models/cvt/modeling_cvt.py#L657 self.layer_norm = torch.nn.LayerNorm(config.embed_dim[-1], eps=config.layer_norm_eps) # No bias as following layer normalisation with bias: self.projection = torch.nn.Linear(config.embed_dim[-1], config.projection_size, bias=False) def forward(self, x: torch.Tensor) -> torch.Tensor: x = self.layer_norm(x) x = self.projection(x) return x class VariableCvtWithProjectionHead(transformers.CvtPreTrainedModel): def __init__(self, config): super().__init__(config) self.cvt = transformers.CvtModel(config, add_pooling_layer=False) self.projection_head = CvtProjectionHead(config) # Initialize weights and apply final processing: self.post_init() def forward( self, pixel_values: Optional[torch.Tensor] = None, output_hidden_states: Optional[bool] = None, return_dict: Optional[bool] = None, ) -> Union[Tuple, ModelOutputWithProjectionEmbedding]: return_dict = return_dict if return_dict is not None else self.config.use_return_dict # Flatten the batch and study_id dimensions: outputs = self.cvt( pixel_values.view(-1, *pixel_values.shape[2:]), output_hidden_states=output_hidden_states, return_dict=return_dict, ) # Flatten h x w: last_hidden_state = torch.flatten(outputs.last_hidden_state, 2) # Project the features for each spatial position to the decoder's hidden size: projection = self.projection_head(torch.permute(last_hidden_state, [0, 2, 1])) # Concatenate the features for each chest X-ray: projection = projection.view(pixel_values.shape[0], -1, projection.shape[-1]) # Derive the attention mask from the pixel values: attention_mask = (pixel_values[:, :, 0, 0, 0] != 0.0).repeat_interleave(last_hidden_state.shape[-1], dim=1) if not return_dict: return projection return ModelOutputWithProjectionEmbedding( last_hidden_state=projection, attention_mask=attention_mask, ) class VariableCXREncoderDecoderModel(VisionEncoderDecoderModel): config_class = VisionEncoderDecoderConfig base_model_prefix = "vision_encoder_decoder" main_input_name = "pixel_values" supports_gradient_checkpointing = True def __init__( self, config: Optional[PretrainedConfig] = None, encoder: Optional[PreTrainedModel] = None, decoder: Optional[PreTrainedModel] = None, ): if decoder: assert decoder.config.add_cross_attention, '"add_cross_attention" must be True for the given decoder' assert decoder.config.is_decoder, '"is_decoder" must be True for the given decoder' if config is None and (encoder is None or decoder is None): raise ValueError("Either a configuration or an encoder and a decoder has to be provided.") if config is None: config = VisionEncoderDecoderConfig.from_encoder_decoder_configs(encoder.config, decoder.config) else: if not isinstance(config, self.config_class): raise ValueError(f"Config: {config} has to be of type {self.config_class}") config.tie_word_embeddings = False # initialize with config PreTrainedModel.__init__(self, config) # Encoder: if encoder is None: encoder = VariableCvtWithProjectionHead(config=config.encoder) # Decoder: if decoder is None: decoder = transformers.BertLMHeadModel(config=config.decoder) self.encoder = encoder self.decoder = decoder if self.encoder.config.to_dict() != self.config.encoder.to_dict(): logger.warning( f"Config of the encoder: {self.encoder.__class__} is overwritten by shared encoder config:" f" {self.config.encoder}" ) if self.decoder.config.to_dict() != self.config.decoder.to_dict(): logger.warning( f"Config of the decoder: {self.decoder.__class__} is overwritten by shared decoder config:" f" {self.config.decoder}" ) self.encoder.config = self.config.encoder self.decoder.config = self.config.decoder # config.add_cross_attention = True # config.is_decoder = True def forward( self, pixel_values: Optional[torch.FloatTensor] = None, decoder_input_ids: Optional[torch.LongTensor] = None, decoder_attention_mask: Optional[torch.BoolTensor] = None, encoder_outputs: Optional[Tuple[torch.FloatTensor]] = None, past_key_values: Optional[Tuple[Tuple[torch.FloatTensor]]] = None, decoder_inputs_embeds: Optional[torch.FloatTensor] = None, labels: Optional[torch.LongTensor] = None, use_cache: Optional[bool] = None, output_attentions: Optional[bool] = None, output_hidden_states: Optional[bool] = None, return_dict: Optional[bool] = None, **kwargs, ) -> Union[Tuple[torch.FloatTensor], Seq2SeqLMOutput]: return_dict = return_dict if return_dict is not None else self.config.use_return_dict kwargs_encoder = {argument: value for argument, value in kwargs.items() if not argument.startswith("decoder_")} kwargs_decoder = { argument[len("decoder_") :]: value for argument, value in kwargs.items() if argument.startswith("decoder_") } if encoder_outputs is None: if pixel_values is None: raise ValueError("You have to specify pixel_values") encoder_outputs = self.encoder( pixel_values, output_hidden_states=output_hidden_states, return_dict=return_dict, **kwargs_encoder, ) # CvT does not support output_attentions. elif isinstance(encoder_outputs, tuple): encoder_outputs = BaseModelOutput(*encoder_outputs) encoder_hidden_states = encoder_outputs[0] decoder_outputs = self.decoder( input_ids=decoder_input_ids, attention_mask=decoder_attention_mask, encoder_hidden_states=encoder_hidden_states, encoder_attention_mask=encoder_outputs.attention_mask, inputs_embeds=decoder_inputs_embeds, output_attentions=output_attentions, output_hidden_states=output_hidden_states, use_cache=use_cache, past_key_values=past_key_values, return_dict=return_dict, **kwargs_decoder, ) # Loss: loss = None if labels is not None: logits = decoder_outputs.logits if return_dict else decoder_outputs[0] loss_fct = CrossEntropyLoss() loss = loss_fct(logits.reshape(-1, self.decoder.config.vocab_size), labels.reshape(-1)) if not return_dict: if loss is not None: return (loss,) + decoder_outputs + encoder_outputs else: return decoder_outputs + encoder_outputs return Seq2SeqLMOutput( loss=loss, logits=decoder_outputs.logits, past_key_values=decoder_outputs.past_key_values, decoder_hidden_states=decoder_outputs.hidden_states, decoder_attentions=decoder_outputs.attentions, cross_attentions=decoder_outputs.cross_attentions, encoder_last_hidden_state=encoder_outputs.last_hidden_state, # encoder_hidden_states=encoder_outputs.hidden_states, # encoder_attentions=encoder_outputs.attentions, ) def prepare_inputs_for_generation( self, input_ids, special_token_ids, past_key_values=None, attention_mask=None, use_cache=None, encoder_outputs=None, **kwargs, ): """ Modification of: https://github.com/huggingface/transformers/blob/main/src/transformers/models/encoder_decoder/modeling_encoder_decoder.py#L660 """ decoder_inputs = self.decoder.prepare_inputs_for_generation(input_ids, past_key_values=past_key_values) decoder_attention_mask = decoder_inputs['attention_mask'] if 'attention_mask' in decoder_inputs else None if not past_key_values: token_type_ids = self.token_ids_to_token_type_ids(input_ids, special_token_ids) else: token_type_ids = self.token_ids_to_token_type_ids_past(input_ids, special_token_ids) input_dict = { 'attention_mask': attention_mask, 'decoder_attention_mask': decoder_attention_mask, 'decoder_input_ids': decoder_inputs['input_ids'], 'decoder_token_type_ids': token_type_ids, 'encoder_outputs': encoder_outputs, 'past_key_values': decoder_inputs['past_key_values'], 'use_cache': use_cache, } return input_dict def token_ids_to_token_type_ids(self, token_ids, special_token_ids, token_type_id_sections=None): """ Extract token type identifiers from the token identifiers. Argument/s: token_ids - token identifiers. special_token_ids - special token identifiers that indicate the separation between sections. token_type_id_section - token type identifier for each section. Returns: token_type_ids - token type identifiers. """ token_type_id_sections = token_type_id_sections if token_type_id_sections is not None else list(range(len(special_token_ids) + 1)) mbatch_size, seq_len = token_ids.shape token_type_ids = torch.full_like(token_ids, token_type_id_sections[0], dtype=torch.long, device=token_ids.device) for i, j in enumerate(special_token_ids): # Find first occurrence of special tokens that indicate the boundary between sections: cols = (token_ids == j).int().argmax(dim=1) rows = torch.arange(mbatch_size, device=token_ids.device) # https://huggingface.co/docs/transformers/model_doc/bert#transformers.BertTokenizer.create_token_type_ids_from_sequences.example cols += 1 # Ensure that the column index is not out of bounds. If 0, then token_id not present. # This is safe as index 0 is always a special token (now equal to 1 due to +1): rows = rows[torch.logical_and(cols != 1, cols < seq_len)] cols = cols[torch.logical_and(cols != 1, cols < seq_len)] # Indices to that correspond to the second sequence: if rows.nelement() != 0: ids = torch.stack([ torch.stack([x, z]) for (x, y) in zip(rows, cols) for z in torch.arange( y, seq_len, device=token_ids.device, ) ]) token_type_ids[ids[:, 0], ids[:, 1]] = token_type_id_sections[i + 1] return token_type_ids def token_ids_to_token_type_ids_past(self, token_ids, special_token_ids, token_type_id_sections=None): """ Extract token type identifiers from the token identifiers if past != None. Argument/s: token_ids - token identifiers. special_token_ids - special token identifiers that indicate the separation between sections. Returns: token_type_ids - token type identifiers. """ token_type_id_sections = token_type_id_sections if token_type_id_sections is not None else list(range(len(special_token_ids) + 1)) token_type_ids = torch.full([token_ids.shape[0], 1], token_type_id_sections[0], dtype=torch.long, device=token_ids.device) # https://huggingface.co/docs/transformers/model_doc/bert#transformers.BertTokenizer.create_token_type_ids_from_sequences.example token_ids = token_ids[:, :-1] for i, j in enumerate(special_token_ids): # Find first occurrence of special token, which indicates the boundary between sections: exists = torch.any(token_ids == j, dim=1, keepdim=True) token_type_ids[exists] = token_type_id_sections[i + 1] return token_type_ids def tokenize_report_teacher_forcing(self, findings: str, impression: str, tokenizer: PreTrainedTokenizerFast, max_len: int): """ Tokenize the reports and creates the inputs and targets for teacher forcing. Argument/s: findings - findings section. impression - impression section. return_token_type_ids - return the token type identifiers. tokenizer - Hugging Face tokenizer. max_len - maximum number of tokens. Returns: decoder_input_ids - the token identifiers for the input of the decoder. decoder_attention_mask - the attention mask for the decoder_input_ids. label_ids - the label token identifiers for the decoder. """ # Prepare the sections for the tokenizer by placing special tokens between each section: report = [f'{tokenizer.bos_token}{i}{tokenizer.sep_token}{j}{tokenizer.eos_token}' for i, j in zip(findings, impression)] # Tokenize the report: tokenized = tokenizer( report, padding='longest', truncation=True, max_length=max_len + 1, # +1 to account for the bias between input and target. return_tensors='pt', return_token_type_ids=False, add_special_tokens=False, ).to(self.device) # Modify for language modelling: batch_dict = { # Labels for the decoder (shifted right by one for autoregression): 'label_ids': tokenized['input_ids'][:, 1:].detach().clone(), # Remove last token identifier to match the sequence length of the labels: 'decoder_input_ids': tokenized['input_ids'][:, :-1], # Attention mask for the decoder_input_ids (remove first token so that the eos_token_id is not considered): 'decoder_attention_mask': tokenized['attention_mask'][:, 1:], } return batch_dict def split_and_decode_sections(self, token_ids, special_token_ids, tokenizer: PreTrainedTokenizerFast): """ Split the token identifiers into sections, then convert the token identifiers into strings. Argument/s: token_ids - token identifiers. special_token_ids - special token identifiers that indicate the end of each section. tokenizer - Hugging Face tokenizer. Returns: token_type_ids - token type identifiers. """ _, seq_len = token_ids.shape # The number of sections is the same as the number of special_token_ids: num_sections = len(special_token_ids) sections = {k: [] for k in range(num_sections)} for i in token_ids: prev_col = 0 for j, k in enumerate(special_token_ids): # The maximum sequence length was exceeded, thus no more tokens: if prev_col >= seq_len: sections[j].append('') continue # Find first occurrence of special tokens that indicate the boundary between sections: col = (i == k).int().argmax().item() # If equal to 0, token was not found, set the column to the sequence length (as the decoder exceeded # the maximum sequence length): if col == 0: col = seq_len # Extract section token identifiers: section_token_ids = i[prev_col:col] prev_col = col section_string = tokenizer.decode(section_token_ids, skip_special_tokens=True) sections[j].append(section_string) return tuple(sections.values())