def get_or_add_image(self, image_descriptor):
        image_part = self._package.image_parts.get_or_add_image_part(
            image_descriptor
        )
        rId = self.relate_to(image_part, RT.IMAGE)
        return rId, image_part.image
Return an (rId, image) 2-tuple for the image identified by
dataset/ETHPy150Open python-openxml/python-docx/docx/parts/document.py/DocumentPart.get_or_add_image