[plotter] Add missing class variables

2 jobs for fix_plotter_storage_class in 22 minutes and 57 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #164569
docker-build
build_linux_36

00:14:54

65.0%
passed #164570
macosx
build_macosx_36

00:22:54

65.0%