Merge pull request #569 from mblondel:release_0.8.3

PiperOrigin-RevId: 597204909

Merge pull request #553 from mblondel:release_0.8.2

PiperOrigin-RevId: 579779709

Merge pull request #543 from mblondel:release_0.8.1

PiperOrigin-RevId: 571461697

Merge pull request #500 from mblondel:release-0.8

PiperOrigin-RevId: 557031423

Merge pull request #434 from mblondel:release_0.7

PiperOrigin-RevId: 535720960

Merge pull request #394 from mblondel:release_0.6

PiperOrigin-RevId: 508371158

Merge pull request #330 from mblondel:release_v0.5.5

PiperOrigin-RevId: 482426902

Merge pull request #300 from mblondel:ot_stop_gradient

PiperOrigin-RevId: 470727718

Merge pull request #262 from fabianp:mblondel-release_0.4.3

PiperOrigin-RevId: 457769261

Merge pull request #239 from mblondel:lbfgs_bug2

PiperOrigin-RevId: 454228985