NTriples serializer does not serialize nested collections

[DJ1TJOO]

When serializing the following in NT:

const nestedCollection = new Collection([lit('nested1'), lit('nested2')])
const collection = new Collection([lit('item1'), nestedCollection, lit('item3')])
const statement = st(sym('http://example.com/subject'), sym('http://example.com/predicate'), collection)

The following output is produced

_:n0 rdf:first "item3".
_:n0 rdf:rest rdf:nill.
_:n1 rdf:first _:n3.
_:n1 rdf:rest _:n0.
_:n4 rdf:first "item1".
_:n4 rdf:rest _:n1.

This is missing the _:n3 blanknode.

Expected:

_:n0 rdf:first "item3".
_:n0 rdf:rest rdf:nill.
_:n2 rdf:first "nested2".
_:n2 rdf:rest rdf:nill.
_:n3 rdf:first "nested1".
_:n3 rdf:rest _:n2.
_:n1 rdf:first _:n3.
_:n1 rdf:rest _:n0.
_:n4 rdf:first "item1".
_:n4 rdf:rest _:n1.
exa:subject exa:predicate _:n4 .

I have fixed this in the phase 3 of my rewrite of the serializer:
#740
DJ1TJOO@315ad33