!1644 dataset: re-fix some format problem in take and split

Merge pull request !1644 from ms_yan/r0.3_doc

mindspore/dataset/engine/datasets.py

@@ -1256,7 +1256,7 @@ class MappableDataset(SourceDataset):
             1. Dataset should not be sharded if split is going to be called. Instead, create a
                DistributedSampler and specify a split to shard after splitting. If dataset is
                sharded after a split, it is strongly recommended to set the same seed in each instance
-                of execution, otherwise each shard may not be part of the same split (see Examples)
+               of execution, otherwise each shard may not be part of the same split (see Examples).
             2. It is strongly recommended to not shuffle the dataset, but use randomize=True instead.
                Shuffling the dataset may not be deterministic, which means the data in each split
                will be different in each epoch. Furthermore, if sharding occurs after split, each