spaCy/spacy/pipeline/simple_ner.py

from typing import List
from thinc.types import Floats2d
from thinc.api import SequenceCategoricalCrossentropy, set_dropout_rate
from thinc.util import to_numpy

from .defaults import default_simple_ner
from ..gold import Example, spans_from_biluo_tags, iob_to_biluo, biluo_to_iob
from ..tokens import Doc
from ..language import component
from ..util import link_vectors_to_models
from .pipes import Pipe


@component("simple_ner", assigns=["doc.ents"], default_model=default_simple_ner)
class SimpleNER(Pipe):
    """Named entity recognition with a tagging model. The model should include
    validity constraints to ensure that only valid tag sequences are returned."""

    def __init__(self, vocab, model):
        self.vocab = vocab
        self.model = model
        self.cfg = {"labels": []}
        self.loss_func = SequenceCategoricalCrossentropy(
            names=self.get_tag_names(),
            normalize=True,
            missing_value=None
        )
        assert self.model is not None

    @property
    def labels(self):
        return self.cfg["labels"]

    @property
    def is_biluo(self):
        return self.model.name.startswith("biluo")

    def add_label(self, label):
        if label not in self.cfg["labels"]:
            self.cfg["labels"].append(label)
 
    def get_tag_names(self):
        if self.is_biluo:
            return (
                [f"B-{label}" for label in self.labels] +
                [f"I-{label}" for label in self.labels] +
                [f"L-{label}" for label in self.labels] +
                [f"U-{label}" for label in self.labels] +
                ["O"]
            )
        else:
            return (
                [f"B-{label}" for label in self.labels] +
                [f"I-{label}" for label in self.labels] +
                ["O"]
            )

    def predict(self, docs: List[Doc]) -> List[Floats2d]:
        scores = self.model.predict(docs)
        return scores

    def set_annotations(self, docs: List[Doc], scores: List[Floats2d], tensors=None):
        """Set entities on a batch of documents from a batch of scores."""
        tag_names = self.get_tag_names()
        for i, doc in enumerate(docs):
            actions = to_numpy(scores[i].argmax(axis=1))
            tags = [tag_names[actions[j]] for j in range(len(doc))]
            if not self.is_biluo:
                tags = iob_to_biluo(tags)
            doc.ents = spans_from_biluo_tags(doc, tags)

    def update(self, examples, set_annotations=False, drop=0.0, sgd=None, losses=None):
        if not any(_has_ner(eg) for eg in examples):
            return 0
        examples = Example.to_example_objects(examples)
        docs = [ex.doc for ex in examples]
        set_dropout_rate(self.model, drop)
        scores, bp_scores = self.model.begin_update(docs)
        loss, d_scores = self.get_loss(examples, scores)
        bp_scores(d_scores)
        if set_annotations:
            self.set_annotations(docs, scores)
        if sgd is not None:
            self.model.finish_update(sgd)
        if losses is not None:
            losses.setdefault("ner", 0.0)
            losses["ner"] += loss
        return loss

    def get_loss(self, examples, scores):
        loss = 0
        d_scores = []
        truths = []
        for eg in examples:
            gold_tags = [(tag if tag != "-" else None) for tag in eg.gold.ner]
            if not self.is_biluo:
                gold_tags = biluo_to_iob(gold_tags)
            truths.append(gold_tags)
        for i in range(len(scores)):
            if len(scores[i]) != len(truths[i]):
                raise ValueError(
                    f"Mismatched output and gold sizes.\n"
                    f"Output: {len(scores[i])}, gold: {len(truths[i])}."
                    f"Input: {len(examples[i].doc)}"
                )
        d_scores, loss = self.loss_func(scores, truths)
        return loss, d_scores

    def begin_training(self, get_examples, pipeline=None, sgd=None, **kwargs):
        self.cfg.update(kwargs)
        if not hasattr(get_examples, '__call__'):
            gold_tuples = get_examples
            get_examples = lambda: gold_tuples
        labels = _get_labels(get_examples())
        for label in _get_labels(get_examples()):
            self.add_label(label)
        labels = self.labels
        n_actions = self.model.attrs["get_num_actions"](len(labels))
        self.model.set_dim("nO", n_actions)
        self.model.initialize() 
        if pipeline is not None:
            self.init_multitask_objectives(get_examples, pipeline, sgd=sgd, **self.cfg)
        link_vectors_to_models(self.vocab)
        self.loss_func = SequenceCategoricalCrossentropy(
            names=self.get_tag_names(),
            normalize=True,
            missing_value=None
        )

        return sgd

    def init_multitask_objectives(self, *args, **kwargs):
        pass


def _has_ner(eg):
    for ner_tag in eg.gold.ner:
        if ner_tag != "-" and ner_tag != None:
            return True
    else:
        return False


def _get_labels(examples):
    labels = set()
    for eg in examples:
        for ner_tag in eg.token_annotation.entities:
            if ner_tag != 'O' and ner_tag != '-':
                _, label = ner_tag.split('-', 1)
                labels.add(label)
    return list(sorted(labels))