Documents belonging to a dataset will be split into different
groups referred to as splits: train, test.
Values:
DATASET_SPLIT_TYPE_UNSPECIFIED (0):
Default value if the enum is not set.
go/protodosdonts#do-include-an-unspecified-value-in-an-enum
DATASET_SPLIT_TRAIN (1):
Identifies the train documents.
DATASET_SPLIT_TEST (2):
Identifies the test documents.
DATASET_SPLIT_UNASSIGNED (3):
Identifies the unassigned documents.