in Classifier-Free Diffusion Guidance.
decoder_guidance_scale is defined as w of equation 2. of Imagen
Paper. Guidance scale is enabled by setting
decoder_guidance_scale > 1. Higher guidance scale encourages to generate images that are closely
linked to the text prompt, usually at the expense of lower image quality.   negative_prompt (str or List[str], optional) —
The prompt or prompts not to guide the image generation. Ignored when not using g