∀ {α : Type u} {β : Type v} [inst : BEq α] [PartialEquivBEq α] {l : List ((_ : α) × β)} {k : α} {fallback : β},
  Std.Internal.List.DistinctKeys l → Std.Internal.List.getValueD k (Std.Internal.List.eraseKey k l) fallback = fallback