paper.   force_upcast (bool, optional, default to True) —
If enabled it will force the VAE to run in float32 for high image resolution pipelines, such as SD-XL. VAE
can be fine-tuned / trained to a lower range without loosing too much precision in which case
force_upcast can be set to False - see: https://huggingface.co/madebyollin/sdxl-vae-fp16-fix    A VAE model with KL loss for encoding images into latents and decoding latent representations