generate_preview method Leave feedback

def generate_preview(self, preview_options):
    ...

    from groupdocs.watermark import Watermarker
    from groupdocs.watermark.options import PreviewOptions, PreviewFormats

    def generate_preview():
        # Supply a writable file stream for each page to render
        def create_page_stream(page_number):
            return open(f"./output-page-{page_number}.png", "wb")

        with Watermarker("./sample.pdf") as watermarker:
            options = PreviewOptions(create_page_stream)
            options.preview_format = PreviewFormats.PNG
            options.page_numbers = [1, 2]
            watermarker.generate_preview(options)

    if __name__ == "__main__":
        generate_preview()
    ```

### See Also
* class [`Watermarker`](/watermark/python-net/groupdocs.watermark/watermarker/)