Function set_seq_override 

pub fn set_seq_override<From, To>()
where
    From: Sequence,
    To: Sequence<Req = From::Req, Rsp = From::Rsp> + Default,

Install a sequence override: wherever From::create_seq() is called, build a To instead.

This is the object half of the factory. UVM registers objects and components separately (uvm_object_utils vs uvm_component_utils) and creates them separately; so does rustdv. Two registries, one factory.