Builds an iterator that terminates once the number of minibatches returned with .next() is equal to a specified number.
Note that a call to .next(num) is counted as a call to return a minibatch regardless of the value of num
This essentially restricts the data to this specified number of minibatches.
Does this MultiDataSetIterator support asynchronous prefetching of multiple MultiDataSet objects?
Most MultiDataSetIterators do, but in some cases it may not make sense to wrap this iterator in an
iterator that does asynchronous prefetching. For example, it would not make sense to use asynchronous
prefetching for the following types of iterators:
(a) Iterators that store their full contents in memory already
(b) Iterators that re-use features/labels arrays (as future next() calls will overwrite past contents)
(c) Iterators that already implement some level of asynchronous prefetching
(d) Iterators that may return different data depending on when the next() method is called