input: Write a python function to create a Student object and test its methods.
  assert student1.get_name() == 'John'
  assert student1.get_age() == 20
  assert student1.get_major() == 'Computer Science'
  assert student2.get_name() == 'Jane'
  assert student2.get_age() == 22
  assert student2.get_major() == 'Mathematics'
  student1.set_name('Johnny')
  assert student1.get_name() == 'Johnny'
  student2.set_age(23)
  assert student2.get_age() == 23
output: class Student:
      def __init__(self, name, age, major):
          self._name = name
          self._age = age
          self._major = major
  
      def get_name(self):
          return self._name
  
      def get_age(self):
          return self._age
  
      def get_major(self):
          return self._major
  
      def set_name(self, name):
          self._name = name
  
      def set_age(self, age):
          self._age = age
  
  def test_student():
      student1 = Student('John', 20, 'Computer Science')
      student2 = Student('Jane', 22, 'Mathematics')
      assert student1.get_name() == 'John'
      assert student1.get_age() == 20
      assert student1.get_major() == 'Computer Science'
      assert student2.get_name() == 'Jane'
      assert student2.get_age() == 22
      assert student2.get_major() == 'Mathematics'
      student1.set_name('Johnny')
      assert student1.get_name() == 'Johnny'
      student2.set_age(23)
      assert student2.get_age() == 23
  
  test_student()