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240 lines
8.6 KiB
Python
240 lines
8.6 KiB
Python
"""Functionality for splitting text."""
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from __future__ import annotations
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import logging
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from abc import ABC, abstractmethod
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from typing import Any, Callable, Iterable, List, Optional
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from langchain.docstore.document import Document
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logger = logging.getLogger()
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class TextSplitter(ABC):
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"""Interface for splitting text into chunks."""
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def __init__(
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self,
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chunk_size: int = 4000,
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chunk_overlap: int = 200,
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length_function: Callable[[str], int] = len,
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):
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"""Create a new TextSplitter."""
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if chunk_overlap > chunk_size:
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raise ValueError(
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f"Got a larger chunk overlap ({chunk_overlap}) than chunk size "
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f"({chunk_size}), should be smaller."
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)
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self._chunk_size = chunk_size
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self._chunk_overlap = chunk_overlap
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self._length_function = length_function
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@abstractmethod
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def split_text(self, text: str) -> List[str]:
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"""Split text into multiple components."""
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def create_documents(
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self, texts: List[str], metadatas: Optional[List[dict]] = None
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) -> List[Document]:
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"""Create documents from a list of texts."""
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_metadatas = metadatas or [{}] * len(texts)
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documents = []
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for i, text in enumerate(texts):
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for chunk in self.split_text(text):
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documents.append(Document(page_content=chunk, metadata=_metadatas[i]))
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return documents
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def _join_docs(self, docs: List[str], separator: str) -> Optional[str]:
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text = separator.join(docs)
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text = text.strip()
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if text == "":
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return None
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else:
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return text
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def _merge_splits(self, splits: Iterable[str], separator: str) -> List[str]:
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# We now want to combine these smaller pieces into medium size
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# chunks to send to the LLM.
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docs = []
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current_doc: List[str] = []
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total = 0
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for d in splits:
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_len = self._length_function(d)
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if total + _len >= self._chunk_size:
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if total > self._chunk_size:
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logger.warning(
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f"Created a chunk of size {total}, "
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f"which is longer than the specified {self._chunk_size}"
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)
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if len(current_doc) > 0:
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doc = self._join_docs(current_doc, separator)
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if doc is not None:
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docs.append(doc)
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# Keep on popping if:
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# - we have a larger chunk than in the chunk overlap
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# - or if we still have any chunks and the length is long
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while total > self._chunk_overlap or (
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total + _len > self._chunk_size and total > 0
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):
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total -= self._length_function(current_doc[0])
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current_doc = current_doc[1:]
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current_doc.append(d)
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total += _len
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doc = self._join_docs(current_doc, separator)
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if doc is not None:
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docs.append(doc)
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return docs
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@classmethod
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def from_huggingface_tokenizer(cls, tokenizer: Any, **kwargs: Any) -> TextSplitter:
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"""Text splitter that uses HuggingFace tokenizer to count length."""
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try:
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from transformers import PreTrainedTokenizerBase
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if not isinstance(tokenizer, PreTrainedTokenizerBase):
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raise ValueError(
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"Tokenizer received was not an instance of PreTrainedTokenizerBase"
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)
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def _huggingface_tokenizer_length(text: str) -> int:
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return len(tokenizer.encode(text))
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except ImportError:
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raise ValueError(
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"Could not import transformers python package. "
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"Please it install it with `pip install transformers`."
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)
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return cls(length_function=_huggingface_tokenizer_length, **kwargs)
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@classmethod
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def from_tiktoken_encoder(
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cls, encoding_name: str = "gpt2", **kwargs: Any
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) -> TextSplitter:
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"""Text splitter that uses tiktoken encoder to count length."""
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try:
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import tiktoken
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except ImportError:
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raise ValueError(
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"Could not import tiktoken python package. "
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"This is needed in order to calculate max_tokens_for_prompt. "
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"Please it install it with `pip install tiktoken`."
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)
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# create a GPT-3 encoder instance
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enc = tiktoken.get_encoding(encoding_name)
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def _tiktoken_encoder(text: str) -> int:
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return len(enc.encode(text))
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return cls(length_function=_tiktoken_encoder, **kwargs)
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class CharacterTextSplitter(TextSplitter):
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"""Implementation of splitting text that looks at characters."""
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def __init__(self, separator: str = "\n\n", **kwargs: Any):
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"""Create a new TextSplitter."""
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super().__init__(**kwargs)
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self._separator = separator
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def split_text(self, text: str) -> List[str]:
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"""Split incoming text and return chunks."""
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# First we naively split the large input into a bunch of smaller ones.
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if self._separator:
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splits = text.split(self._separator)
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else:
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splits = list(text)
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return self._merge_splits(splits, self._separator)
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class RecursiveCharacterTextSplitter(TextSplitter):
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"""Implementation of splitting text that looks at characters.
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Recursively tries to split by different characters to find one
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that works.
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"""
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def __init__(self, separators: Optional[List[str]] = None, **kwargs: Any):
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"""Create a new TextSplitter."""
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super().__init__(**kwargs)
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self._separators = separators or ["\n\n", "\n", " ", ""]
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def split_text(self, text: str) -> List[str]:
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"""Split incoming text and return chunks."""
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final_chunks = []
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# Get appropriate separator to use
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separator = self._separators[-1]
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for _s in self._separators:
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if _s == "":
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separator = _s
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break
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if _s in text:
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separator = _s
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break
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# Now that we have the separator, split the text
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if separator:
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splits = text.split(separator)
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else:
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splits = list(text)
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# Now go merging things, recursively splitting longer texts.
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_good_splits = []
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for s in splits:
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if len(s) < self._chunk_size:
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_good_splits.append(s)
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else:
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if _good_splits:
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merged_text = self._merge_splits(_good_splits, separator)
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final_chunks.extend(merged_text)
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_good_splits = []
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other_info = self.split_text(s)
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final_chunks.extend(other_info)
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if _good_splits:
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merged_text = self._merge_splits(_good_splits, separator)
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final_chunks.extend(merged_text)
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return final_chunks
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class NLTKTextSplitter(TextSplitter):
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"""Implementation of splitting text that looks at sentences using NLTK."""
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def __init__(self, separator: str = "\n\n", **kwargs: Any):
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"""Initialize the NLTK splitter."""
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super().__init__(**kwargs)
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try:
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from nltk.tokenize import sent_tokenize
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self._tokenizer = sent_tokenize
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except ImportError:
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raise ImportError(
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"NLTK is not installed, please install it with `pip install nltk`."
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)
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self._separator = separator
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def split_text(self, text: str) -> List[str]:
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"""Split incoming text and return chunks."""
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# First we naively split the large input into a bunch of smaller ones.
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splits = self._tokenizer(text)
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return self._merge_splits(splits, self._separator)
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class SpacyTextSplitter(TextSplitter):
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"""Implementation of splitting text that looks at sentences using Spacy."""
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def __init__(
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self, separator: str = "\n\n", pipeline: str = "en_core_web_sm", **kwargs: Any
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):
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"""Initialize the spacy text splitter."""
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super().__init__(**kwargs)
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try:
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import spacy
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except ImportError:
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raise ImportError(
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"Spacy is not installed, please install it with `pip install spacy`."
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)
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self._tokenizer = spacy.load(pipeline)
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self._separator = separator
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def split_text(self, text: str) -> List[str]:
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"""Split incoming text and return chunks."""
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splits = (str(s) for s in self._tokenizer(text).sents)
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return self._merge_splits(splits, self._separator)
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