public static void ShowTrainersInCourse()
        {
            Console.Clear();
            CourseDb            cDb     = new CourseDb();
            TrainersPerCourseDb tpcDb   = new TrainersPerCourseDb();
            List <Course>       courses = cDb.GetCourses();

            if (courses.Count != 0)
            {
                Console.WriteLine("Please select a course by using its number on the list: \n");
                ShowList(courses, "Courses");

                bool result = Int32.TryParse(Console.ReadLine(), out int courseID);
                while (!result || (courseID < 1 || courseID > courses.Count))
                {
                    Console.Write($"Wrong input! Please select using numbers from 1 to {courses.Count} ");
                    result = Int32.TryParse(Console.ReadLine(), out courseID);
                }
                Console.Clear();

                List <Trainer> trainersPerCourse = tpcDb.GetTrainersPerCourse(courseID);
                ShowList(trainersPerCourse, $"Trainers Per This Course");
            }
            else
            {
                Console.WriteLine("There are no trainers or courses yet");
            }
        }