input: Write a python function to create a list of Student objects and sort them by age in ascending order.
  assert sort_students_by_age([Student("Alice", 23, "A"), Student("Bob", 21, "B"), Student("Charlie", 22, "C")]) == [Student("Bob", 21, "B"), Student("Charlie", 22, "C"), Student("Alice", 23, "A")]
  assert sort_students_by_age([Student("David", 25, "A"), Student("Eve", 20, "B"), Student("Frank", 24, "C")]) == [Student("Eve", 20, "B"), Student("Frank", 24, "C"), Student("David", 25, "A")]
output: class Student:
      def __init__(self, name, age, grade):
          self.name = name
          self.age = age
          self.grade = grade
          
      def __eq__(self, other):
          return self.name == other.name and self.age == other.age and self.grade == other.grade
  
      def __repr__(self):
          return f"Student({self.name!r}, {self.age!r}, {self.grade!r})"
  
  def sort_students_by_age(students):
      return sorted(students, key=lambda student: student.age)