How to use the pytesseract.image_to_pdf_or_hocr function in pytesseract

def test_image_to_pdf_or_hocr(test_file, extension):
    result = image_to_pdf_or_hocr(test_file, extension=extension)

    if extension is 'pdf':
        if IS_PYTHON_2:
            assert isinstance(result, str)
            result = str(result).strip()
            assert result.startswith('%PDF')
            assert result.endswith('EOF')
        else:
            assert isinstance(result, bytes)

    if extension is 'hocr':
        assert isinstance(result, bytes)  # type
        result = result.decode('utf-8') if IS_PYTHON_2 else str(result, 'utf-8')
        result = str(result).strip()
        assert result.startswith('')

def _image_to_pdf(path):
        image = Image.open(path)
        pdf = pytesseract.image_to_pdf_or_hocr(image, extension='pdf')

        filename = '.'.join(os.path.basename(path).split('.')[:-1]) + '.pdf'
        dirname = os.path.dirname(path)

        path = filedialog.asksaveasfilename(title='Save Converted PDF As', defaultextension='.pdf',
                                            initialdir=dirname, initialfile=filename,
                                            filetypes=[('PDF files', '*.pdf'), ('all files', '.*')])
        if path == '' or path is None:
            return
        with open(path, 'wb') as out:
            out.write(pdf)
        return path

def convert_png(png):
        ocr_output = pytesseract.image_to_pdf_or_hocr(png, extension='pdf')
        with open(png + '.pdf', 'wb') as f:
            f.write(ocr_output)
            return png + '.pdf'