input: Write a python function to get the day of the week from a date string.
  assert get_day_of_week('20/02/2023') == 'Monday'
  assert get_day_of_week('01/01/2000') == 'Saturday'
  assert get_day_of_week('31/12/1999') == 'Friday'
output: def get_day_of_week(date_string):
      import datetime
      date_obj = datetime.datetime.strptime(date_string, '%d/%m/%Y')
      return date_obj.strftime('%A')