CRUD Backend API and Debugging

Design and implement a CRUD backend system similar to a chatgpt interface using Python. You need to complete the following tasks: Debug a given endpoint. Implement standard CRUD operations including Create, Read, Update, and Delete. Choose and configure a database (SQLite3 is recommended). Run and test the APIs on localhost to ensure the frontend code can properly call the backend. Please provide code that fulfills all the above requirements and relevant test cases. Input No specific input requirements; the system should automatically run and test based on built-in conditions. Output The expected result of each CRUD operation must be demonstrated. Data Scale No specific limits, primarily assessing code implementation and CRUD logic. Test Cases Create a new user and verify successful creation. Update user information and verify the update. Delete a user and verify deletion. Retrieve the user list and verify completeness. Debug the given endpoint and ensure it correctly returns data.