def _preprocess_text(self, documents: np.ndarray) -> List[str]:
        r"""Basic preprocessing of text.

        Steps:
            * Replace \n and \t with whitespace
            * Only keep alpha-numerical characters
        """
        cleaned_documents = [doc.replace("\n", " ") for doc in documents]
        cleaned_documents = [doc.replace("\t", " ") for doc in cleaned_documents]
        if self.language == "english":
            cleaned_documents = [re.sub(r"[^A-Za-z0-9 ]+", "", doc) for doc in cleaned_documents]
        cleaned_documents = [doc if doc != "" else "emptydoc" for doc in cleaned_documents]
        return cleaned_documents
Basic preprocessing of text.

        Steps:
            * Replace \n and \t with whitespace
            * Only keep alpha-numerical characters
        
bertopic/_bertopic.py