text: Title: Add numpy doc strings 
  Body: Add numpy style doc strings to all functions apart from the main.py file. 
  
  
  
  
  
  <details>
  <summary>Checklist</summary>
  
  - [X] `gpt_engineer/ai.py`
  > • For each function in this file, add or replace the existing docstring with a numpy-style docstring. The docstring should include a brief description of the function, a list of parameters with their types and descriptions, and a description of the return value.
  
  - [X] `gpt_engineer/chat_to_files.py`
  > • For each function in this file, add or replace the existing docstring with a numpy-style docstring. The docstring should include a brief description of the function, a list of parameters with their types and descriptions, and a description of the return value.
  
  - [X] `gpt_engineer/collect.py`
  > • For each function in this file, add or replace the existing docstring with a numpy-style docstring. The docstring should include a brief description of the function, a list of parameters with their types and descriptions, and a description of the return value.
  
  - [X] `gpt_engineer/db.py`
  > • For each function in this file, add or replace the existing docstring with a numpy-style docstring. The docstring should include a brief description of the function, a list of parameters with their types and descriptions, and a description of the return value.
  
  - [X] `gpt_engineer/learning.py`
  > • For each function in this file, add or replace the existing docstring with a numpy-style docstring. The docstring should include a brief description of the function, a list of parameters with their types and descriptions, and a description of the return value.
  
  </details>
  