// for the function arguments are read from `specs`, but the type and shape
  // information for the function returns are inferred by the shape refiner in
  // ImporterBase.
  absl::StatusOr<mlir::FunctionType> InferMainFunctionType(
      const GraphImportConfig& specs, mlir::MLIRContext* context,
      absl::InlinedVector<OutputTensor, 4>* arg_nodes,
      absl::InlinedVector<OutputTensor, 4>* ret_nodes);