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Embedding Models

In this tutorial we will be going through the embedding models that can be used in KeyBERT. Having the option to choose embedding models allow you to leverage pre-trained embeddings that suit your use-case.

Sentence Transformers

You can select any model from sentence-transformers here and pass it through KeyBERT with model:

from keybert import KeyBERT
kw_model = KeyBERT(model="all-MiniLM-L6-v2")

Or select a SentenceTransformer model with your own parameters:

from sentence_transformers import SentenceTransformer

sentence_model = SentenceTransformer("all-MiniLM-L6-v2")
kw_model = KeyBERT(model=sentence_model)

🤗 Hugging Face Transformers

To use a Hugging Face transformers model, load in a pipeline and point to any model found on their model hub (https://huggingface.co/models):

from transformers.pipelines import pipeline

hf_model = pipeline("feature-extraction", model="distilbert-base-cased")
kw_model = KeyBERT(model=hf_model)

Tip!

These transformers also work quite well using sentence-transformers which has a number of optimizations tricks that make using it a bit faster.

Flair

Flair allows you to choose almost any embedding model that is publicly available. Flair can be used as follows:

from flair.embeddings import TransformerDocumentEmbeddings

roberta = TransformerDocumentEmbeddings('roberta-base')
kw_model = KeyBERT(model=roberta)

You can select any 🤗 transformers model here.

Moreover, you can also use Flair to use word embeddings and pool them to create document embeddings. Under the hood, Flair simply averages all word embeddings in a document. Then, we can easily pass it to KeyBERT in order to use those word embeddings as document embeddings:

from flair.embeddings import WordEmbeddings, DocumentPoolEmbeddings

glove_embedding = WordEmbeddings('crawl')
document_glove_embeddings = DocumentPoolEmbeddings([glove_embedding])

kw_model = KeyBERT(model=document_glove_embeddings)

Spacy

Spacy is an amazing framework for processing text. There are many models available across many languages for modeling text.

To use Spacy's non-transformer models in KeyBERT:

import spacy

nlp = spacy.load("en_core_web_md", exclude=['tagger', 'parser', 'ner', 'attribute_ruler', 'lemmatizer'])

kw_model = KeyBERT(model=nlp)

Using spacy-transformer models:

import spacy

spacy.prefer_gpu()
nlp = spacy.load("en_core_web_trf", exclude=['tagger', 'parser', 'ner', 'attribute_ruler', 'lemmatizer'])

kw_model = KeyBERT(model=nlp)

If you run into memory issues with spacy-transformer models, try:

import spacy
from thinc.api import set_gpu_allocator, require_gpu

nlp = spacy.load("en_core_web_trf", exclude=['tagger', 'parser', 'ner', 'attribute_ruler', 'lemmatizer'])
set_gpu_allocator("pytorch")
require_gpu(0)

kw_model = KeyBERT(model=nlp)

Universal Sentence Encoder (USE)

The Universal Sentence Encoder encodes text into high dimensional vectors that are used here for embedding the documents. The model is trained and optimized for greater-than-word length text, such as sentences, phrases or short paragraphs.

Using USE in KeyBERT is rather straightforward:

import tensorflow_hub
embedding_model = tensorflow_hub.load("https://tfhub.dev/google/universal-sentence-encoder/4")
kw_model = KeyBERT(model=embedding_model)

Gensim

For Gensim, KeyBERT supports its gensim.downloader module. Here, we can download any model word embedding model to be used in KeyBERT. Note that Gensim is primarily used for Word Embedding models. This works typically best for short documents since the word embeddings are pooled.

import gensim.downloader as api
ft = api.load('fasttext-wiki-news-subwords-300')
kw_model = KeyBERT(model=ft)

Custom Backend

If your backend or model cannot be found in the ones currently available, you can use the keybert.backend.BaseEmbedder class to create your own backend. Below, you will find an example of creating a SentenceTransformer backend for KeyBERT:

from keybert.backend import BaseEmbedder
from sentence_transformers import SentenceTransformer

class CustomEmbedder(BaseEmbedder):
    def __init__(self, embedding_model):
        super().__init__()
        self.embedding_model = embedding_model

    def embed(self, documents, verbose=False):
        embeddings = self.embedding_model.encode(documents, show_progress_bar=verbose)
        return embeddings

# Create custom backend
distilbert = SentenceTransformer("paraphrase-MiniLM-L6-v2")
custom_embedder = CustomEmbedder(embedding_model=distilbert)

# Pass custom backend to keybert
kw_model = KeyBERT(model=custom_embedder)
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