Скрыть <iostream> в деталях реализации

#ifndef WORKER_H
#define WORKER_H
 
#include <iostream>
#include <memory>
#include <string>
 
#include "Data.h"
#include "Enums.h"
 
class Worker {
  using string = std::string;
 
 public:
  Worker(const string &name = "Default", const string &surname = "Default",
         int age = 0, Sex sex = kMale, Position position = kCleaner,
         const string &phone_number = "Default", int day = 0, int month = 0,
         int year = 0);
  ~Worker();
 
  void ShowWorkerInfo() const;
 
 private:
  static string ConvertSex(Sex sex);
  static string ConvertPosition(Position position);
 
  string name_ = "Default";
  string surname_ = "Default";
  int age_ = 0;
  Sex sex_ = kMale;
  Position position_ = kCleaner;
  string telephone_number_ = "Default";
 
  std::unique_ptr<Data> birthday_ = std::unique_ptr<Data>(new Data);
 
  template <typename T>
  void WriteData(const string &text, T) const;
};
 
template <typename T>
void Worker::WriteData(const std::string &text, T data) const {
  std::cout << text << data << std::endl;
}
 
#endif  // WORKER_H

template <typename T>
void WriteData(const std::string &text, T data, std::ostream & os)
{
    os << text << data << std::endl;
}