epoch!

			epoch!(learner, phase[, dataiter])

Train learner for one epoch on dataiter . Iterates through
dataiter and step! s for each batch/item.

If no data iterator is passed in, use learner.data[phasedataiter(phase)] .

Extending

The default implementation iterates over every batch in dataiter
and calls step! for each. This behavior can be overloaded
by implementing epoch!(learner, ::MyPhase, dataiter) .

If you’re implementing a custom epoch! method, it is recommended
you make use of runepoch to get begin and end events as well
as proper handling of CancelEpochException s.

See the default implementation for reference.