Bug: YAML format not quoting ":"

[Shadow-Devil]

Today I was working with the YAML format and unfortunatly, dataweave produced an incorrect YAML file:

%dw 2.0
output application/yaml
---
a: ":"

produces following output:

 %YAML 1.2
 ---
 a: :

which is not correct. It should quote the ":".
As expected it also doesn't accept this yaml file as an input.
I think there is also no way of quoting all output strings when producing YAML (at least I didn't find any).