Update pytorch_single_node_and_gpu.py (flyteorg#419)

Embedding a video to outline the Pytorch training process for single-node single GPUs.

cookbook/case_studies/ml_training/mnist_classifier/pytorch_single_node_and_gpu.py

@@ -10,7 +10,9 @@
 that supports *PyTorch-Ignite* or *PyTorch Lightening* support, but this is not critical). One can request for a GPU, simply
 by setting GPU="1" resource request and then at runtime, the GPU will be provisioned.
 
-In this example, we'll see how we can create any PyTorch model, train it using Flyte and a specialized container. 
+In this example, we'll see how we can create any PyTorch model, train it using Flyte and a specialized container. The following video will outline the basics of this process.
+
+..  youtube:: sJrERMVtxL4
 """
 
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