These are internal only.
getFunctionName(FUN, originalDots, ..., overrideCall, isPipe).digestRasterLayer(object, length, algo, quick)
A function
passing the ... from outer function, which will include potential arguments to the FUN
A character string indicating a different (not "Cache") function name to search for. Mostly so that this works with deprecated "cache".
Logical. If the call to getFunctionName is coming from a pipe, there is more information available. Specifically, ._lhs which is already a call.