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from collections import OrderedDict
from operator import itemgetter
from transformers.utils import ModelOutput
import torch
from torch import nn
from typing import Dict, List, Tuple, Optional
from dataclasses import dataclass
from transformers import BertPreTrainedModel, BertModel, BertTokenizerFast
ALL_POS = ['DET', 'NOUN', 'VERB', 'CCONJ', 'ADP', 'PRON', 'PUNCT', 'ADJ', 'ADV', 'SCONJ', 'NUM', 'PROPN', 'AUX', 'X', 'INTJ', 'SYM']
ALL_PREFIX_POS = ['SCONJ', 'DET', 'ADV', 'CCONJ', 'ADP', 'NUM']
ALL_SUFFIX_POS = ['none', 'ADP_PRON', 'PRON']
ALL_FEATURES = [
('Gender', ['none', 'Masc', 'Fem', 'Fem,Masc']),
('Number', ['none', 'Sing', 'Plur', 'Plur,Sing', 'Dual', 'Dual,Plur']),
('Person', ['none', '1', '2', '3', '1,2,3']),
('Tense', ['none', 'Past', 'Fut', 'Pres', 'Imp'])
]
@dataclass
class MorphLogitsOutput(ModelOutput):
prefix_logits: torch.FloatTensor = None
pos_logits: torch.FloatTensor = None
features_logits: List[torch.FloatTensor] = None
suffix_logits: torch.FloatTensor = None
suffix_features_logits: List[torch.FloatTensor] = None
def detach(self):
return MorphLogitsOutput(self.prefix_logits.detach(), self.pos_logits.detach(), [logits.deatch() for logits in self.features_logits], self.suffix_logits.detach(), [logits.deatch() for logits in self.suffix_features_logits])
@dataclass
class MorphTaggingOutput(ModelOutput):
loss: Optional[torch.FloatTensor] = None
logits: Optional[MorphLogitsOutput] = None
hidden_states: Optional[Tuple[torch.FloatTensor]] = None
attentions: Optional[Tuple[torch.FloatTensor]] = None
@dataclass
class MorphLabels(ModelOutput):
prefix_labels: Optional[torch.FloatTensor] = None
pos_labels: Optional[torch.FloatTensor] = None
features_labels: Optional[List[torch.FloatTensor]] = None
suffix_labels: Optional[torch.FloatTensor] = None
suffix_features_labels: Optional[List[torch.FloatTensor]] = None
def detach(self):
return MorphLabels(self.prefix_labels.detach(), self.pos_labels.detach(), [labels.detach() for labels in self.features_labels], self.suffix_labels.detach(), [labels.detach() for labels in self.suffix_features_labels])
def to(self, device):
return MorphLabels(self.prefix_labels.to(device), self.pos_labels.to(device), [feat.to(device) for feat in self.features_labels], self.suffix_labels.to(device), [feat.to(device) for feat in self.suffix_features_labels])
class BertMorphTaggingHead(nn.Module):
def __init__(self, config):
super().__init__()
self.config = config
self.num_prefix_classes = len(ALL_PREFIX_POS)
self.num_pos_classes = len(ALL_POS)
self.num_suffix_classes = len(ALL_SUFFIX_POS)
self.num_features_classes = list(map(len, map(itemgetter(1), ALL_FEATURES)))
# we need a classifier for prefix cls and POS cls
# the prefix will use BCEWithLogits for multiple labels cls
self.prefix_cls = nn.Linear(config.hidden_size, self.num_prefix_classes)
# and pos + feats will use good old cross entropy for single label
self.pos_cls = nn.Linear(config.hidden_size, self.num_pos_classes)
self.features_cls = nn.ModuleList([nn.Linear(config.hidden_size, len(features)) for _, features in ALL_FEATURES])
# and suffix + feats will also be cross entropy
self.suffix_cls = nn.Linear(config.hidden_size, self.num_suffix_classes)
self.suffix_features_cls = nn.ModuleList([nn.Linear(config.hidden_size, len(features)) for _, features in ALL_FEATURES])
def forward(
self,
hidden_states: torch.Tensor,
labels: Optional[MorphLabels] = None):
# run each of the classifiers on the transformed output
prefix_logits = self.prefix_cls(hidden_states)
pos_logits = self.pos_cls(hidden_states)
suffix_logits = self.suffix_cls(hidden_states)
features_logits = [cls(hidden_states) for cls in self.features_cls]
suffix_features_logits = [cls(hidden_states) for cls in self.suffix_features_cls]
loss = None
if labels is not None:
# step 1: prefix labels loss
loss_fct = nn.BCEWithLogitsLoss(weight=(labels.prefix_labels != -100).float())
loss = loss_fct(prefix_logits, labels.prefix_labels)
# step 2: pos labels loss
loss_fct = nn.CrossEntropyLoss()
loss += loss_fct(pos_logits.view(-1, self.num_pos_classes), labels.pos_labels.view(-1))
# step 2b: features
for feat_logits,feat_labels,num_features in zip(features_logits, labels.features_labels, self.num_features_classes):
loss += loss_fct(feat_logits.view(-1, num_features), feat_labels.view(-1))
# step 3: suffix logits loss
loss += loss_fct(suffix_logits.view(-1, self.num_suffix_classes), labels.suffix_labels.view(-1))
# step 3b: suffix features
for feat_logits,feat_labels,num_features in zip(suffix_features_logits, labels.suffix_features_labels, self.num_features_classes):
loss += loss_fct(feat_logits.view(-1, num_features), feat_labels.view(-1))
return loss, MorphLogitsOutput(prefix_logits, pos_logits, features_logits, suffix_logits, suffix_features_logits)
class BertForMorphTagging(BertPreTrainedModel):
def __init__(self, config):
super().__init__(config)
self.bert = BertModel(config, add_pooling_layer=False)
self.dropout = nn.Dropout(config.hidden_dropout_prob)
self.morph = BertMorphTaggingHead(config)
# Initialize weights and apply final processing
self.post_init()
def forward(
self,
input_ids: Optional[torch.Tensor] = None,
attention_mask: Optional[torch.Tensor] = None,
token_type_ids: Optional[torch.Tensor] = None,
position_ids: Optional[torch.Tensor] = None,
labels: Optional[MorphLabels] = None,
head_mask: Optional[torch.Tensor] = None,
inputs_embeds: Optional[torch.Tensor] = None,
output_attentions: Optional[bool] = None,
output_hidden_states: Optional[bool] = None,
return_dict: Optional[bool] = None,
):
return_dict = return_dict if return_dict is not None else self.config.use_return_dict
bert_outputs = self.bert(
input_ids,
attention_mask=attention_mask,
token_type_ids=token_type_ids,
position_ids=position_ids,
head_mask=head_mask,
inputs_embeds=inputs_embeds,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
hidden_states = bert_outputs[0]
hidden_states = self.dropout(hidden_states)
loss, logits = self.morph(hidden_states, labels)
if not return_dict:
return (loss,logits) + bert_outputs[2:]
return MorphTaggingOutput(
loss=loss,
logits=logits,
hidden_states=bert_outputs.hidden_states,
attentions=bert_outputs.attentions,
)
def predict(self, sentences: List[str], tokenizer: BertTokenizerFast, padding='longest'):
# tokenize the inputs and convert them to relevant device
inputs = tokenizer(sentences, padding=padding, truncation=True, return_tensors='pt')
inputs = {k:v.to(self.device) for k,v in inputs.items()}
# calculate the logits
logits = self.forward(**inputs, return_dict=True).logits
return parse_logits(inputs['input_ids'].tolist(), sentences, tokenizer, logits)
def parse_logits(input_ids: List[List[int]], sentences: List[str], tokenizer: BertTokenizerFast, logits: MorphLogitsOutput):
prefix_logits, pos_logits, feats_logits, suffix_logits, suffix_feats_logits = \
logits.prefix_logits, logits.pos_logits, logits.features_logits, logits.suffix_logits, logits.suffix_features_logits
prefix_predictions = (prefix_logits > 0.5).int().tolist() # Threshold at 0.5 for multi-label classification
pos_predictions = pos_logits.argmax(axis=-1).tolist()
suffix_predictions = suffix_logits.argmax(axis=-1).tolist()
feats_predictions = [logits.argmax(axis=-1).tolist() for logits in feats_logits]
suffix_feats_predictions = [logits.argmax(axis=-1).tolist() for logits in suffix_feats_logits]
# create the return dictionary
# for each sentence, return a dict object with the following files { text, tokens }
# Where tokens is a list of dicts, where each dict is:
# { pos: str, feats: dict, prefixes: List[str], suffix: str | bool, suffix_feats: dict | None}
special_toks = tokenizer.all_special_tokens
ret = []
for sent_idx,sentence in enumerate(sentences):
input_id_strs = tokenizer.convert_ids_to_tokens(input_ids[sent_idx])
# iterate through each token in the sentence, ignoring special tokens
tokens = []
for token_idx,token_str in enumerate(input_id_strs):
if token_str in special_toks: continue
if token_str.startswith('##'):
tokens[-1]['token'] += token_str[2:]
continue
tokens.append(dict(
token=token_str,
pos=ALL_POS[pos_predictions[sent_idx][token_idx]],
feats=get_features_dict_from_predictions(feats_predictions, (sent_idx, token_idx)),
prefixes=[ALL_PREFIX_POS[idx] for idx,i in enumerate(prefix_predictions[sent_idx][token_idx]) if i > 0],
suffix=get_suffix_or_false(ALL_SUFFIX_POS[suffix_predictions[sent_idx][token_idx]]),
))
if tokens[-1]['suffix']:
tokens[-1]['suffix_feats'] = get_features_dict_from_predictions(suffix_feats_predictions, (sent_idx, token_idx))
ret.append(dict(text=sentence, tokens=tokens))
return ret
def get_suffix_or_false(suffix):
return False if suffix == 'none' else suffix
def get_features_dict_from_predictions(predictions, idx):
ret = {}
for (feat_idx, (feat_name, feat_values)) in enumerate(ALL_FEATURES):
val = feat_values[predictions[feat_idx][idx[0]][idx[1]]]
if val != 'none':
ret[feat_name] = val
return ret
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