foldLeft

fun <A, B, C> ERROR CLASS: Symbol not found for SortedMap<A, B>.foldLeft(b: ERROR CLASS: Symbol not found for SortedMap<A, C>, f: (ERROR CLASS: Symbol not found for SortedMap<A, C>, Map.Entry<A, B>) -> ERROR CLASS: Symbol not found for SortedMap<A, C>): ERROR CLASS: Symbol not found for SortedMap<A, C>