if (failed(InitializeFromFuncAttributes())) {
    return fused_func_op_.emitError()
           << "Expected function attributes were not set on the function "
              "encapsulating the composite op";
  }

  num_gates_ = couple_input_forget_gates_ ? 3 : 4;

  input_ = fused_func_op_.getArgument(0);
  bias_ = fused_func_op_.getArgument(2);

  weight_ = fused_func_op_.getArgument(1);

class ConvertLSTMCellSimpleToFusedLSTM {
 public:
  explicit ConvertLSTMCellSimpleToFusedLSTM(mlir::func::FuncOp fused_func_op)
      : fused_func_op_(fused_func_op),
        couple_input_forget_gates_(false),
        builder_(fused_func_op.getBody()) {}

  // not copyable.
  ConvertLSTMCellSimpleToFusedLSTM(const ConvertLSTMCellSimpleToFusedLSTM&) =
      delete;