//// Copyright (c) 2006, Brian Frank and Andy Frank// Licensed under the Academic Free License version 3.0//// History:// 11 Jan 06 Brian Frank Creation//**** UnknownSlotErr indicates an attempt to access a non-existent slot.**const class UnknownSlotErr : Err {**** Construct with specified error message and optional root cause.**new make(Str msg := "", Err? cause := null) }