Extend KeepIndex to Vector indices

Using an example from the documentation:

julia> ca = ComponentArray(a=5, b=[4, 1], c=(a=2, b=[6, 30]))
ComponentVector{Int64}(a = 5, b = [4, 1], c = (a = 2, b = [6, 30]))

julia> ca[KeepIndex(:b)]
ComponentVector{Int64}(b = [4, 1])

julia> ca[KeepIndex(1)]
ComponentVector{Int64}(a = 5)

julia> ca[KeepIndex(2:3)]
ComponentVector{Int64}(b = [4, 1])

julia> ca[KeepIndex([2,3])]
ERROR: TypeError: in Type, in parameter, expected Type, got a value of type Vector{Int64}

How hard would it be to extend the KeepIndex functionality to more general types of indices?

Start by reading the KeepIndex implementation and the documentation example shown in this issue. Reproduce the KeepIndex([2, 3]) failure, then determine which general index types should be supported and how success should be verified without the current TypeError.