BEFORE_MINIBATCH = 1
AFTER_MINIBATCH = 2

BEFORE_TRAIN_MINIBATCH = 3
AFTER_TRAIN_MINIBATCH = 4

BEFORE_EVAL_MINIBATCH = 5
AFTER_EVAL_MINIBATCH = 6

BEFORE_TRAIN = 7
AFTER_TRAIN = 8

BEFORE_EVAL = 9
AFTER_EVAL = 10

BEFORE_EPOCH = 11
AFTER_EPOCH = 12
