error: no member function declared in class

I keep getting the following errors from my code:

(line 58) error: no ‘std::string Person::Modify_Person(Person)’ member function declared in class ‘Person’ In function ‘int main()’:

(line 113) error: ‘Modify_Person’ was not declared in this scope

Here is the code:

#include <iostream>
#include <string>

using namespace std;

void PassByByValue(int num2){

  cout << "You are in PassByValue()" << endl;

  num2++;

}
class Person{
    int age;
    string name;
    int height;
    int weight;
public:

    Person(){

    }

    Person(string name){
        this->name=name;
    }

    string getName(){
    return this->name;
    }

    void setAge(int age){
    this->age=age;
    }