def obs_list
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
48def obs_list(~T: Data, r: Stack<T> & List<&2, T>) -> Stack<T> & E.Obs<T>:
49 (q, xs) = r
50 (q, E.OList{xs})