def obs_nat
import bend-collections@1.0.0.0/src/containers/stack.bend as Stackimport Base
import bend-collections@1.0.0.0/src/containers/types/stack.bend as E
40def obs_nat(~T: Data, r: Stack<T> & Nat) -> Stack<T> & E.Obs<T>:
41 (q, n) = r
42 (q, E.ONat{n})