[DelayedSample(Set)] make load and delayed_attributes private

2 jobs for fix-delayed-samples-setattr in 4 minutes and 5 seconds (queued for 4 seconds)
Status Name Job ID Coverage
  Build
passed build_linux_37 #218964
docker

00:03:38

passed build_macosx_37 #218963
macosx

00:04:01