Problem with "Building a Multi-Node Graph-Based AI Agent Framework for Complex Task Automation"

I tried to reproduce the code of the paper "https://www.marktechpost.com/2025/07/26/building-a-multi-node-graph-based-ai-agent-framework-for-complex-task-automation/", but what is the function GraphAgent() in this file? I cannot see it anywhere.

Here is the link for the code: https://github.com/Marktechpost/AI-Tutorial-Codes-Included/blob/main/graph_agent_framework_with_gemini_Marktechpost.ipynb