How to enable Scheme evaluation?

[ceving]

When I press M-n v v in the following code block

```{scheme}
(+ 1 2)
```

I get the following error:

polymode-eval-chunk: Undefined ‘polymode-eval-region-function’ in buffer parse.md[scheme]

How to define the missing function?

[prosoitos]

I'm having the same problem with Python code blocks.

[jcubic]

I use C-c C-e that is bind to (scheme-send-definition) in scheme mode, it sends expression to Scheme process.