Convenience function to construct sub-C-sets

[epatters]

It would be convenient to have a function that constructs a sub-C-set of a C-set. Specifically, I am imagining a generic function subobject with a method

subobject(x::ACSet, parts::NamedTuple)

to be called like

x = Graph()
...
f = subobject(x, (V=[...], E=[...]))

and returning a monomorphism f with codom(f) == x.