langchain/text_splitter.py/NLTKTextSplitter/split_text
class NLTKTextSplitter:    def split_text(self, text: str) -> List[str]:
        """Split incoming text and return chunks."""
        # First we naively split the large input into a bunch of smaller ones.
        splits = self._tokenizer(text)
        return self._merge_splits(splits, self._separator)