input: Write a python function to calculate the salary of an employee using the Employee class.
  assert Employee("John", 20, 40).calculate_salary() == 800
  assert Employee("Jane", 15, 35).calculate_salary() == 525
  assert Employee("Doe", 25, 10).calculate_salary() == 250
output: class Employee:
      def __init__(self, name, hourly_wage, hours_worked):
          self.name = name
          self.hourly_wage = hourly_wage
          self.hours_worked = hours_worked
  
      def calculate_salary(self):
          return self.hourly_wage * self.hours_worked