Recommended way to query whether jupyterlab-myst is available in _repr_markdown

[VolkerH]

Hi,

I would like to make some classes more notebook friendly by adding a _repr_markdown_ method to them.

I would like to auto-detect whether myst markdown is supported within the _repr_markdown_ method and either return simple markdown or some more fancy Myst markdown (if supported).

Is there a recommended way to query whether I am running in a context where a Myst Markdown renderer is active? (Maybe through some environment variable)