def obs_list
import bend-collections@1.0.0.0/src/containers/deque.bend as Dequeimport Base
import bend-collections@1.0.0.0/src/containers/types/deque.bend as E
122def obs_list(~T: Data, r: Deque<T> & List<&2, T>) -> Deque<T> & E.Obs<T>:
123 (d, xs) = r
124 (d, E.OList{xs})