public interface IExampleInterface<in TIn, out TOut>
    {
        public TOut MyMethod(TIn param);
    }

    public class MyExampleInheritor : IExampleInterface<B, B>
    {
        public B MyMethod(B param)
        {
            Debug.LogWarning($"Param is {param}");
            return (C)param;
        }
    }

    public class UseExample
    {
        public UseExample()
        {
            var inst = new MyExampleInheritor();
            var result = (C) inst.MyMethod(new D());
            Debug.LogWarning($"Return is {result}");

        }
    }

    public class A
    {
        public override string ToString()
        {
            return $"class A";
        }
    }

    public class B : A
    {
        public override string ToString()
        {
            return $"class B";
        }
    }

    public class C : B
    {
        public override string ToString()
        {
            return $"class C";
        }
    }

    public class D : C
    {
        public override string ToString()
        {
            return $"class D";
        }
    }