Does Isolator support C# local functions? [closed]

I have a method with a local function that I would like to be able to fake. In the example below, I would like to be able to say something like Isolate.NonPublic.WhenCalled(someObject, "LocalHelperMethod").WillReturn("fakeData"), but the method is not found. Is there a way to do this?

public string MethodUnderTest()

{

   // Do stuff.

  return someValue;

  string LocalHelperMethod() // Private to the containing method.

  {

      // Desire to fake this return.

  }

}