rendered paste body#ifndef LIST_H#define LIST_H#include "node.h"#include <iostream>using namespace std;class List { private: Node* head, *tail; int list_size; public: List() { this->head = NULL; this->tail = NULL; list_size = 0; } void insert(int); int& operator[](int) const; int size() const; void reverse(void);};ostream& operator<<(ostream& out, const List& listObj) { int i = 0; for(i;i<listObj.size(); i++) out << listObj.operator [](i); return out;}#endif/* The Error:Error 4 error LNK2005: "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl operator<<(class std::basic_ostream<char,struct std::char_traits<char> > &,class List const &)" (??6@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@std@@AAV01@ABVList@@@Z) already defined in list.obj main.obj*/