class MyClass : public ExternalBase // This class is from external framework and framework requires it to derive from this class.
{
    int doSomePrivateThing(int );
public:

    virtual int DoSomething(int );
    virtual ~MyClass();
}

int MyClass::doSomePrivateThing(int )
{
    // do some private task
}

int MyClass::DoSomething(int n)
{
    // Do MyClass Specific task
    int k = doSomePrivateThing(n);
    return ExternalBase::DoSomething(k); // This function depends on external system resources.
                                         // Probably try to communicate with remote server
                                         // or attempt access Storage or Display device etc.
}

MyClass::~MyClass()
{}