Register_raw is like Register except you get to deal with the whole pipe. This is useful if, e.g., your model_of_update function can fail, so that you'd like to filter items out from the result pipe.
Register_raw
Register
model_of_update
Version_i : sig ... end
val rpc : (Version_i.query, Version_i.state, Version_i.update, Version_i.error) Async_rpc_kernel.Rpc.State_rpc.t