"formerType": {
"@id": "as:formerType",
"@type": "@id"
},
Problem
"@type": "@id" is base-relative, not vocab-relative; therefore, terms such as the AS2 activity types will not expand. For example, "formerType": "Note" should expand according to the definition of Note, which is https://www.w3.org/ns/activitystreams#Note, but this definition does nothing unless the term formerType is vocab-relative.
Solution
Make formerType vocab-relative by defining it as "@type": "@vocab".
"formerType": {
"@id": "as:formerType",
"@type": "@vocab"
},