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from __future__ import annotations
try:
from typing import Self
except ImportError:
from typing_extensions import Self
import torch
from torch import nn
from sentence_transformers.models.Module import Module
class LSTM(Module):
"""Bidirectional LSTM running over word embeddings."""
config_keys: list[str] = ["word_embedding_dimension", "hidden_dim", "num_layers", "dropout", "bidirectional"]
config_file_name: str = "lstm_config.json"
def __init__(
self,
word_embedding_dimension: int,
hidden_dim: int,
num_layers: int = 1,
dropout: float = 0,
bidirectional: bool = True,
):
super().__init__()
self.word_embedding_dimension = word_embedding_dimension
self.hidden_dim = hidden_dim
self.num_layers = num_layers
self.dropout = dropout
self.bidirectional = bidirectional
self.embeddings_dimension = hidden_dim
if self.bidirectional:
self.embeddings_dimension *= 2
self.encoder = nn.LSTM(
word_embedding_dimension,
hidden_dim,
num_layers=num_layers,
dropout=dropout,
bidirectional=bidirectional,
batch_first=True,
)
def forward(self, features):
token_embeddings = features["token_embeddings"]
sentence_lengths = torch.clamp(features["sentence_lengths"], min=1)
packed = nn.utils.rnn.pack_padded_sequence(
token_embeddings, sentence_lengths.cpu(), batch_first=True, enforce_sorted=False
)
packed = self.encoder(packed)
unpack = nn.utils.rnn.pad_packed_sequence(packed[0], batch_first=True)[0]
features.update({"token_embeddings": unpack})
return features
def get_word_embedding_dimension(self) -> int:
return self.embeddings_dimension
def save(self, output_path: str, *args, safe_serialization: bool = True, **kwargs) -> None:
self.save_config(output_path)
# Saving LSTM models with Safetensors does not work unless the weights are on CPU
# See https://github.com/huggingface/sentence-transformers/pull/2722
device = next(self.parameters()).device
self.cpu()
self.save_torch_weights(output_path, safe_serialization=safe_serialization)
self.to(device)
@classmethod
def load(
cls,
model_name_or_path: str,
subfolder: str = "",
token: bool | str | None = None,
cache_folder: str | None = None,
revision: str | None = None,
local_files_only: bool = False,
**kwargs,
) -> Self:
hub_kwargs = {
"subfolder": subfolder,
"token": token,
"cache_folder": cache_folder,
"revision": revision,
"local_files_only": local_files_only,
}
config = cls.load_config(model_name_or_path=model_name_or_path, **hub_kwargs)
model = cls(**config)
model = cls.load_torch_weights(model_name_or_path=model_name_or_path, model=model, **hub_kwargs)
return model