return func.emitError() << "Mismatched number of inputs and outputs.";
  }
  auto values_type = GetInputType(func, 0);
  if (!values_type || !mlir::isa<StringType>(values_type.getElementType())) {
    return func.emitError() << "First input should be a string tensor";
  }
  auto row_splits_type = GetInputType(func, 1);
  if (!row_splits_type ||
      !mlir::isa<IntegerType>(row_splits_type.getElementType())) {