struct Flyweight(T, alias makeFunc, alias disposeFunc, alias idNames, const FlyweightOptions options = FlyweightOptions.none)
static 
void
unloadAll
out
{
    
    foreach (id; EnumMembers!(ID)[0 .. $ - 1])
    {
        assert (!isLoaded(id));
    }
    assert (!isAnyLoaded);
}
 if (
isCallable!makeFunc && 
isCallable!disposeFunc
)
 
Manually unload all loaded instances and reset reference counts/loaded flags.