def chunk(filename, binary=None, from_page=0, to_page=100000,
          lang="Chinese", callback=None, **kwargs):
    """
        Supported file formats are docx, pdf, txt.
    """
    doc = {
        "docnm_kwd": filename,
        "title_tks": rag_tokenizer.tokenize(re.sub(r"\.[a-zA-Z]+$", "", filename))
    }
    doc["title_sm_tks"] = rag_tokenizer.fine_grained_tokenize(doc["title_tks"])
    pdf_parser = None
    sections = []
    # is it English
    eng = lang.lower() == "english"  # is_english(sections)

    if re.search(r"\.docx$", filename, re.IGNORECASE):
        callback(0.1, "Start to parse.")
        chunks = Docx()(filename, binary)
        callback(0.7, "Finish parsing.")
        return tokenize_chunks(chunks, doc, eng, None)

    elif re.search(r"\.pdf$", filename, re.IGNORECASE):
        pdf_parser = Pdf()
        if kwargs.get("layout_recognize", "DeepDOC") == "Plain Text":
            pdf_parser = PlainParser()
        for txt, poss in pdf_parser(filename if not binary else binary,
                                    from_page=from_page, to_page=to_page, callback=callback)[0]:
            sections.append(txt + poss)

    elif re.search(r"\.txt$", filename, re.IGNORECASE):
        callback(0.1, "Start to parse.")
        txt = get_text(filename, binary)
        sections = txt.split("\n")
        sections = [s for s in sections if s]
        callback(0.8, "Finish parsing.")

    elif re.search(r"\.(htm|html)$", filename, re.IGNORECASE):
        callback(0.1, "Start to parse.")
        sections = HtmlParser()(filename, binary)
        sections = [s for s in sections if s]
        callback(0.8, "Finish parsing.")

    elif re.search(r"\.doc$", filename, re.IGNORECASE):
        callback(0.1, "Start to parse.")
        binary = BytesIO(binary)
        doc_parsed = parser.from_buffer(binary)
        sections = doc_parsed['content'].split('\n')
        sections = [s for s in sections if s]
        callback(0.8, "Finish parsing.")

    else:
        raise NotImplementedError(
            "file type not supported yet(doc, docx, pdf, txt supported)")


    # Remove 'Contents' part
    remove_contents_table(sections, eng)

    make_colon_as_title(sections)
    bull = bullets_category(sections)
    chunks = hierarchical_merge(bull, sections, 5)
    if not chunks:
        callback(0.99, "No chunk parsed out.")

    return tokenize_chunks(["\n".join(ck)
                           for ck in chunks], doc, eng, pdf_parser)

        Supported file formats are docx, pdf, txt.
    
rag/app/laws.py