code: public NiceXWPFDocument generate() throws IOException {
          ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
          this.write(byteArrayOutputStream);
          this.close();
          return new NiceXWPFDocument(new ByteArrayInputStream(byteArrayOutputStream.toByteArray()));
      }
docs: 生成一个新的流文档
  
  @return
  @throws IOException
  @since 1.3.0