Possible content of "contexts" in Edge exceptions

[#1]

Can you give me an example that demonstrates the possible structure/content of "contexts" property from an Edge exception? I tried to find one, but as I can see it usually returns an empty (array) structure.

For example, when I try to get an non-existing developer attribute's value then Edge returns an error like this:

{
  "code": "organizations.keymanagement.AttributeDoesntExist",
  "message": "Attribute does not exist",
  "contexts": []
}

Also, just to confirm, only >= 400 and <500 HTTP codes can contains "Edge exceptions" like this?

[#2]

Nobody has more information about this?