Loads data from a dataset and returns mini-batches of data.
Parameters
----------
dataset : Dataset
Source dataset. Note that numpy and mxnet arrays can be directly used
as a Dataset.
batch_size : int
Size of mini-batch.
shuffle : bool
Whether to shuffle the samples.
sampler : Sampler
The sampler to use. Either specify sampler or shuffle, not both.
last_batch : {'keep', 'discard', 'rollover'}
How to handle the last batch if batch_size does not evenly divide
`len(dataset)`.
keep - A batch with less samples than previous batches is returned.
discard - The last batch is discarded if its incomplete.
rollover - The remaining samples are rolled over to the next epoch.
batch_sampler : Sampler
A sampler that returns mini-batches. Do not specify batch_size,
shuffle, sampler, and last_batch if batch_sampler is specified.