Sage support

I noticed that when I pair a notebook with a sagemath kernel with a markdown file, code blocks are not converted to code cells. Here is a minimal example:

---
jupyter:
  jupytext:
    formats: ipynb,md
    text_representation:
      extension: .md
      format_name: markdown
      format_version: '1.2'
      jupytext_version: 1.9.1
  kernelspec:
    display_name: SageMath 9.2
    language: sage
    name: sagemath
---

```sage
print("Hello world")
```

After converting with jupytext --to ipynb exmplae.md the code block ends up in a markdown cell. With a python kernel and a python code block the conversion works as expected, resulting in a code cell.

The documentation states that

Code snippets are turned into code cells in Jupyter as soon as they have an explicit language, when that language is supported in Jupyter.

But sage is supported by Jupyter. Maybe what is meant here is that the language must be supported by Jupytext? Since sage is not listed under supported languages. I would be grateful for a clarification.

[frcl]

Works fine. Thank you very much! This is a huge improvement for me.

[frcl]

Well, sage is just a thin wrapper around python with some snytaxtic sugar added with a preparser and lots of libraries. In general sage code will not execute when called directly with python, so the ambiguous extension .py may cause some confusion. It is relatively simple to convert the sage script to a python script, but converting back may be problematic.

The language_info is in fact equivalent in all my sage notebooks, except for version numbers.