I just asked your question to Copilot, here is his answer:
This issue is caused by a missing dependency inside the official SageMath 10.9
Docker image. The last cell of the sagemath_examples.ipynb notebook uses
Cython (via %%cython), which requires the Python development headers in order
to compile the generated C code.
Inside the 10.9 Docker image, the file python.h is not present, which means
that the corresponding package (typically python3-dev or python3.X-dev) was not
installed when the image was built. As a result, any Cython cell that needs to
compile C extensions will fail with the error:
fatal error: Python.h: No such file or directory
This is not a user error and not related to the notebook itself. It is a
packaging issue in the Docker image: the Python headers are required for Cython
examples to work, but they are currently missing.
The Docker image likely needs to be rebuilt with the appropriate Python
development package installed. For example, on Debian/Ubuntu-based images,
installing:
apt-get install python3-dev
(or the specific versioned package matching the Python version inside the
container) would resolve the issue.
Until the image is updated, any Cython-based examples in the official notebook
will fail inside the 10.9 Docker container.