Step - combine

combine(list) appends a second list to the list a traverser holds. Duplicates and order are kept. The incoming value must be a list (see List Functions for the input and argument rules shared by all list functions).

graphersal> g.V().values("name").fold().combine(["dave", "marko"])
[marko, vadas, lop, josh, ripple, peter, dave, marko]

graphersal> g.V().out().out().path().by("name").combine(["dave"])
[marko, josh, ripple, dave]
[marko, josh, lop, dave]

graphersal> g.inject([1, 2]).combine(__.constant([2, 3]))
[1, 2, 2, 3]

Rust: combine(vec!["dave"]) and combine_traversal(__::constant(vec![2, 3])).

The set counterpart, which keeps each element once, is merge.