map8<R extends Object>  method 
Implementation
@pragma('vm:prefer-inline')
TResolvableOption<Object> map8<R extends Object>(R Function(T) mapper) {
  return map((e) => e.map7((e) => mapper(e as T))).reduce();
}@pragma('vm:prefer-inline')
TResolvableOption<Object> map8<R extends Object>(R Function(T) mapper) {
  return map((e) => e.map7((e) => mapper(e as T))).reduce();
}