list-accumulating keys with a default value of the empty list
module Key : sig ... end
val set : t ‑> 'a Key.t ‑> 'a Core_kernel__.Import.list ‑> t
val find : t ‑> 'a Key.t ‑> 'a Core_kernel__.Import.list
val change : t ‑> 'a Key.t ‑> f:('a Core_kernel__.Import.list ‑> 'a Core_kernel__.Import.list) ‑> t