input: Write a python function to calculate the grade average of a student.
  assert Student("Alice", 20, [90, 80, 70, 60]).get_grade_average() == 75.0
  assert Student("Bob", 22, [100, 95, 85]).get_grade_average() == 93.33
  assert Student("Charlie", 19, [60, 70, 80, 90, 100]).get_grade_average() == 80.0
output: class Student:
      def __init__(self, name, age, grades):
          self.name = name
          self.age = age
          self.grades = grades
  
      def get_grade_average(self):
          return round(sum(self.grades) / len(self.grades), 2)