fix sphinx warnings

4 jobs for frame-container-load-subset in 11 minutes and 50 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #186747
docker
build_linux_36

00:04:25

80.0%
passed #186748
docker
build_linux_37

00:04:17

80.0%
passed #186745
macosx
build_macosx_36

00:11:50

80.0%
passed #186746
macosx
build_macosx_37

00:11:45

80.0%