getAttr throws a no consensus type error when traversing to a vertex set

GSQL
#1

I am looking to programatically access the attributes of an edge between two defined vertex sets.

I can do the following traversal and accum absolutely fine (assuming two vertex types called Day and Week and an edge type contained with an integer attribute num):

SumAccum<INT> @@total;
__ = SELECT d FROM Day:d -(contained:c)- Week:w 
    ACCUM @@total += c.getAttr("num", "INT");

If I pass a specific Week vertex into my query and convert it to a vertex set

CREATE QUERY test(VERTEX<Week> week)...
week_vvs = {week};

I get the error no consensus type for term c.getAttr("num", "INT") when running basically the same traversal:

SumAccum<INT> @@total;
__ = SELECT d FROM Day:d -(contained:c)- week_vvs:w 
    ACCUM @@total += c.getAttr("num", "INT");

Is this the expected behaviour? I can access the attribute num by doing c.num perfectly fine, its just the getAttr that causes the problem. I’m unsure as to why it works for the generic node type, but not for a vertex set of that node type.