Runtime.ImportModuleError: Unable to import module 'lambda_function': cannot import name '_extra' from partially initialized module 'pymupdf' (most likely due to a circular import) (/opt/python/pymupd

The error you're encountering suggests there might be an issue with how the pymupdf library is being imported or initialized within your Lambda function environment. This could be due to a circular import problem or incompatibility between the installed version and your Lambda runtime.

To resolve this issue, you can try the following steps:

1. Ensure that you're using a version of pymupdf that is compatible with Python 3.11 and AWS Lambda's environment. Check the pymupdf documentation for version compatibility information.

2. When creating your layer, make sure the directory structure is correct. The Python libraries should be in a directory named 'python' at the root of your ZIP file. For example:

   python/
     pymupdf/
     pandas/
   

3. Try creating a fresh virtual environment matching your Lambda's Python version (3.11), install the required packages there, and then create your layer ZIP from that environment. This can help ensure all dependencies are properly resolved.

4. If possible, try simplifying your code to isolate the issue. Create a minimal example that only imports pymupdf to see if the problem persists.

5. Check if there are any conflicting dependencies between pymupdf and other libraries you're using. Sometimes, different libraries may require different versions of shared dependencies.

6. Consider using a Lambda container image instead of layers if the issue persists. This gives you more control over the execution environment.

7. If the problem continues, you might need to reach out to the pymupdf maintainers to see if there are known issues with the library in Lambda environments.

Remember, while AWS CodeBuild can be helpful for building layers, it's not the only way to create them. You can still create layers locally and upload them to Lambda if you ensure the correct structure and compatibility.

If these steps don't resolve the issue, you may need to provide more details about your Lambda function code and how you're importing and using pymupdf within it for further troubleshooting.

Sources
Lambda layer for Python packages not working | AWS re:Post
Unable to Import Lambda Function Module: No module named 'lambda_function' | AWS re:Post