"contain 'host_func' function.";

  if (op->getNumOperands() != func.getFunctionType().getNumInputs())
    return op.emitError()
           << "'host_func' has " << func.getFunctionType().getNumInputs()
           << " inputs and '_XlaHostComputeMlir' has " << op->getNumOperands()
           << " operands.  Number of operands/inputs should be the same.";

  // TODO(jpienaar): Expand to support inputs.
  mlir::func::FuncOp main = module->lookupSymbol<mlir::func::FuncOp>("main");
  QCHECK(main) << "No 'main' function specified.";
  if (main.getFunctionType().getNumInputs() != 0)
    LOG(QFATAL) << "NYI: Only nullary functions supported.";

  // Convert to flatbuffer.
  std::string serialized_flatbuffer;
  tflite::FlatbufferExportOptions options;

  virtual llvm::StringRef GetCompositeOpName() { return kLstmCellSimple; }

  // Rewrite the func body with constructed fused lstm.
  LogicalResult RewriteFunc();

  int GetNumInputs() { return n_input_; }

 protected:
  // verify input func op arguments/attributes and initialize internal state.
  virtual LogicalResult InitializeFromFuncAttributes();
  virtual LogicalResult Initialize();