input: Write a python function to create a list of Student objects and sort them by their marks.
  assert sorted_students([('Alice', 21, 88), ('Bob', 22, 75), ('Charlie', 20, 92)]) == [('Charlie', 20, 92), ('Alice', 21, 88), ('Bob', 22, 75)]
  assert sorted_students([('David', 23, 70), ('Eva', 22, 85), ('Frank', 21, 95)]) == [('Frank', 21, 95), ('Eva', 22, 85), ('David', 23, 70)]
  assert sorted_students([('George', 24, 60), ('Helen', 25, 77), ('Ian', 23, 83)]) == [('Ian', 23, 83), ('Helen', 25, 77), ('George', 24, 60)]
output: def sorted_students(student_tuples):
      class Student:
          def __init__(self, name, age, marks):
              self.name = name
              self.age = age
              self.marks = marks
          
          def __repr__(self):
              return f"({self.name}, {self.age}, {self.marks})"
      
      students = [Student(name, age, marks) for name, age, marks in student_tuples]
      students.sort(key=lambda student: student.marks, reverse=True)
      return [(student.name, student.age, student.marks) for student in students]