Please use FileSystem tools to finish the following task:

### Task Description

ThreeStudio is a comprehensive codebase that implements various diffusion-based text-to-3D models, including NeRF-based rendering stage and diffusion guidance stage. Your task is to explore the codebase and identify the specific file that defines the guidance functionality for the Zero123 model.

### Task

What is the output of `guidance_out`, returned by the code at line 137 in `threestudio/systems/zero123.py`?

Clearly state the structure of it and where you find the answer (file and line numbers).Write your answer in a file named `answer.txt` in the test directory root. Do not add extra explanation or formatting beyond what is required by the task.
