.FastAIblocklossfn

			blocklossfn(predblock, yblock)

Construct a loss function that compares a batch of model outputs ŷs and encoded targets ys and returns a scalar loss.

For example for block = OneHotLabel(classes) (i.e. an encoded Label(classes)), we have blocklossfn(block, block) == Flux.Losses.logitcrossentropy.