Problem about create new dog C++

#pragma once
#include <list>

class SerializedObject;

class Dog
{
public:
	static const int SID = 1;
	static Dog* NewDog() { return nullptr; }
	static void DeleteAll() {}
	static Dog* CreateFromSO(SerializedObject* tSO) { return nullptr; }
	static Dog* FindDogFromID(int tID) { return nullptr; }

	int mAge = 0;

	SerializedObject* Serialize() { return nullptr; }// Only we know how to smoosh ourselves.  Everyone knows what an SO is

private:
	int mObjectID = 0; // Which Dog object am I?
	Dog() {} // Can't make a person without going through our factory

	static std::list<Dog*> sAllDogs;

};