message: fix strings.split
diff: @@ -22,6 +22,7 @@ from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import gen_string_ops
  +from tensorflow.python.ops import gen_array_ops
  from tensorflow.python.ops import string_ops
  from tensorflow.python.ops.ragged import ragged_array_ops
  from tensorflow.python.ops.ragged import ragged_math_ops
  @@ -630,6 +631,8 @@ def strings_split_v1(input=None, sep=None, maxsplit=-1, # pylint: disable=redef
  if result_type == "SparseTensor" and input.shape.rank == 1:
  return string_ops.string_split_v2(input, sep=sep, maxsplit=maxsplit)
  + if result_type == "SparseTensor" and input.shape.rank==0:
  + input = gen_array_ops.expand_dims(input, 0)
  ragged_result = string_split_v2(input, sep=sep, maxsplit=maxsplit)
  if result_type == "SparseTensor":
  return ragged_result.to_sparse()
  