[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 Job ID Name Coverage
  Build
passed #218964
docker
build_linux_37

00:03:38

passed #218963
macosx
build_macosx_37

00:04:01