Flask 如何实现 Word 文件上传并预览？

from flask import Flask, request, redirect, url_for, send_filefrom werkzeug.utils import secure_filenameapp = Flask(__name__)@app.route('/', methods=['GET', 'POST'])def upload_file():    if request.method == 'POST':        file = request.files['file']        filename = secure_filename(file.filename)        file.save(filename)        # 使用第三方服务进行预览        # ...        # 使用 PDF 转换器进行预览        # ...        return redirect(url_for('preview', filename=filename))    return '''        <h1>上传文件</h1>        <form method=post enctype=multipart/form-data>          <input type=file name=file>          <input type=submit value=Upload>        </form>    '''@app.route('/preview/<filename>')def preview(filename):    # 根据预览类型返回相应的文件    # ...    return send_file(filename)if __name__ == '__main__':    app.run()