Various Chroma pipeline issues

[dxqb]

Describe the bug

Some minor issues that I have found while using the Chroma pipeline for the first time:

• if sentencepiece is not installed, you get a quite cryptic error message. Other pipelines such as Flux give you a nice error message that sentencepiece has to be installed
• The config attributes {'guidance_embeds': False, 'pooled_projection_dim': 768} were passed to ChromaTransformer2DModel, but are not expected and will be ignored. Please verify your config.json configuration file.
  Chroma does not use CLIP, only T5, so there is no pooled projection. and does not use a guidance embedding as Flux - but I guess this is an issue with the config file, not the diffusers pipeline
• this code

  diffusers/src/diffusers/pipelines/chroma/pipeline_chroma.py

  Line 806 in 03c3f69

  mu = calculate_shift(

  seems unnecessary, because dynamic timestep shifting is disabled in Chroma's scheduler config: https://huggingface.co/lodestones/Chroma1-HD/blob/main/scheduler/scheduler_config.json
  confirmed by the actual timesteps that are used:
  (Pdb) timesteps tensor([1000., 975., 950., 925., 900., 875., 850., 825., 800., 775., 750., 725., 700., 675., 650., 625., 600., 575., 550., 525., 500., 475., 450., 425., 400., 375., 350., 325., 300., 275., 250., 225., 200., 175., 150., 125., 100., 75., 50., 25.], device='cuda:0')
• Chroma's official repo is lodestones/Chroma1-HD now. This could be updated in your pipeline example code: https://huggingface.co/docs/diffusers/main/api/pipelines/chroma

Reproduction

run the sample code here https://huggingface.co/docs/diffusers/main/api/pipelines/chroma

Logs

System Info

diffusers HEAD, python 3.11.11

Who can help?

No response

[DN6]

Hi @dxqbYD Thanks for flagging. Would you be able to open a PR to resolve the issues you've listed? Feel free to tag me for a review.

[dxqb]

I cannot do sentencepiece, I don't know where the nice message from other models comes from.
I could remove the timestep shifting code, if you agree that this wasn't intentional for some reason, and change the repo.