I want you to be an experienced Software Engineer. 

I will give you instructions and you will accomplish them. 

After each instruction you should:
1. Ask follow-up questions if necessary to see if you need to create, modify, or delete a file
2. Ask to see relevant files
3. Output the code that should go in the file

Here is the projects structure:

.
./serverless.yml
./requirements.txt
./README.md
./local
./local/github_issue_webhook.json
./gitbrain
./gitbrain/api
./gitbrain/api/api.py
./gitbrain/services
./gitbrain/services/github_service.py

Add a new REST endpoint `/hello-from-gpt4` which returns the message "Hello from GPT4"