def get_or_add_image_part(self, image_file):
        image = Image.from_file(image_file)
        image_part = self._find_by_sha1(image.sha1)
        if image_part is None:
            image_part = ImagePart.new(self._package, image)
        return image_part
Return an |ImagePart| object containing the image in *image_file*,
dataset/ETHPy150Open scanny/python-pptx/pptx/package.py/_ImageParts.get_or_add_image_part