def __call__(
        self,
        batch_size: int = 1,
        generator: Optional[torch.Generator] = None,
        num_inference_steps: int = 1000,
        output_type: Optional[str] = "pil",
        return_dict: bool = True,
        **kwargs,
    ) -> Union[ImagePipelineOutput, Tuple]:
        r"""
        Args:
            batch_size (`int`, *optional*, defaults to 1):
                The number of images to generate.
            generator (`torch.Generator`, *optional*):
                A [torch generator](https://pytorch.org/docs/stable/generated/torch.Generator.html) to make generation
                deterministic.
            num_inference_steps (`int`, *optional*, defaults to 1000):
                The number of denoising steps. More denoising steps usually lead to a higher quality image at the
                expense of slower inference.
            output_type (`str`, *optional*, defaults to `"pil"`):
                The output format of the generate image. Choose between
                [PIL](https://pillow.readthedocs.io/en/stable/): `PIL.Image.Image` or `np.array`.
            return_dict (`bool`, *optional*, defaults to `True`):
                Whether or not to return a [`~pipeline_utils.ImagePipelineOutput`] instead of a plain tuple.

        Returns:
            [`~pipeline_utils.ImagePipelineOutput`] or `tuple`: [`~pipelines.utils.ImagePipelineOutput`] if
            `return_dict` is True, otherwise a `tuple. When returning a tuple, the first element is a list with the
            generated images.
        """
        message = (
            "Please make sure to instantiate your scheduler with `predict_epsilon` instead. E.g. `scheduler ="
            " DDPMScheduler.from_pretrained(<model_id>, predict_epsilon=True)`."
        )
        predict_epsilon = deprecate("predict_epsilon", "0.10.0", message, take_from=kwargs)

        if predict_epsilon is not None:
            new_config = dict(self.scheduler.config)
            new_config["predict_epsilon"] = predict_epsilon
            self.scheduler._internal_dict = FrozenDict(new_config)

        if generator is not None and generator.device.type != self.device.type and self.device.type != "mps":
            message = (
                f"The `generator` device is `{generator.device}` and does not match the pipeline "
                f"device `{self.device}`, so the `generator` will be ignored. "
                f'Please use `torch.Generator(device="{self.device}")` instead.'
            )
            deprecate(
                "generator.device == 'cpu'",
                "0.11.0",
                message,
            )
            generator = None

        # Sample gaussian noise to begin loop
        image_shape = (batch_size, self.unet.in_channels, self.unet.sample_size, self.unet.sample_size)
        if self.device.type == "mps":
            # randn does not work reproducibly on mps
            image = torch.randn(image_shape, generator=generator)
            image = image.to(self.device)
        else:
            image = torch.randn(image_shape, generator=generator, device=self.device)

        # set step values
        self.scheduler.set_timesteps(num_inference_steps)

        for t in self.progress_bar(self.scheduler.timesteps):
            # 1. predict noise model_output
            model_output = self.unet(image, t).sample

            # 2. compute previous image: x_t -> x_t-1
            image = self.scheduler.step(
                model_output, t, image, generator=generator, predict_epsilon=predict_epsilon
            ).prev_sample

        image = (image / 2 + 0.5).clamp(0, 1)
        image = image.cpu().permute(0, 2, 3, 1).numpy()
        if output_type == "pil":
            image = self.numpy_to_pil(image)

        if not return_dict:
            return (image,)

        return ImagePipelineOutput(images=image)

        Args:
            batch_size (`int`, *optional*, defaults to 1):
                The number of images to generate.
            generator (`torch.Generator`, *optional*):
                A [torch generator](https://pytorch.org/docs/stable/generated/torch.Generator.html) to make generation
                deterministic.
            num_inference_steps (`int`, *optional*, defaults to 1000):
                The number of denoising steps. More denoising steps usually lead to a higher quality image at the
                expense of slower inference.
            output_type (`str`, *optional*, defaults to `"pil"`):
                The output format of the generate image. Choose between
                [PIL](https://pillow.readthedocs.io/en/stable/): `PIL.Image.Image` or `np.array`.
            return_dict (`bool`, *optional*, defaults to `True`):
                Whether or not to return a [`~pipeline_utils.ImagePipelineOutput`] instead of a plain tuple.

        Returns:
            [`~pipeline_utils.ImagePipelineOutput`] or `tuple`: [`~pipelines.utils.ImagePipelineOutput`] if
            `return_dict` is True, otherwise a `tuple. When returning a tuple, the first element is a list with the
            generated images.
        
promptist/diffusers/src/diffusers/pipelines/ddpm/pipeline_ddpm.py