Leaf ops do self-reset.

embed python compose op

add implicit compose op

more tests

change ImagefolderDV2 name

change ds.transforms.vision to ds.vision

change batch api to match map api more closely

compose op changes

test_pylint

remove compose op from vision, move to transform module, refactor map and batch to use column_order

fix line lengths

fix spacing

reverse a few changes

Signed-off-by: leonwanghui <leon.wanghui@huawei.com>