Potentially 2 LR Schedulers used for Object Detection Tutorial

[JoanneLin168]

Link to tutorial: https://pytorch.org/tutorials/intermediate/torchvision_tutorial.html

Hi there, I am following the object detection tutorial and have copied the necessary files from pytorch/vision/main/references/detection/. When inspecting the engine.train_one_epoch() function, I see that it creates a LR scheduler (LinearLR) there and calls lr_scheduler.step() inside train_one_epoch(), however in the tutorial it also creates its own LR scheduler (StepLR) in the main script, and also calls lr_scheduler.step() within the training loop.

Is this meant to be the case or should the tutorial be updated?

cc @datumbox @nairbv @fmassa @NicolasHug @YosuaMichael