input: Write a python function to get available tickets and assert that the returned tickets list is correct.
  assert get_tickets() == [ {'ticket_id': 1, 'event': 'Concert', 'price': 50}, {'ticket_id': 2, 'event': 'Play', 'price': 30} ]
  assert get_tickets() == [ {'ticket_id': 3, 'event': 'Movie', 'price': 20}, {'ticket_id': 4, 'event': 'Exhibition', 'price': 40} ]
  
  Write a python function to create a reservation and assert that the reservation is correctly created.
  assert create_reservation(1) == {'ticket_id': 1, 'status': 'reserved'}
  assert create_reservation(2) == {'ticket_id': 2, 'status': 'reserved'}
  
  Write a python function to cancel a reservation and assert that the reservation is correctly cancelled.
  assert cancel_reservation(1) == {'ticket_id': 1, 'status': 'cancelled'}
  assert cancel_reservation(2) == {'ticket_id': 2, 'status': 'cancelled'}
output: def get_tickets():
      return [
          {'ticket_id': 1, 'event': 'Concert', 'price': 50},
          {'ticket_id': 2, 'event': 'Play', 'price': 30},
          {'ticket_id': 3, 'event': 'Movie', 'price': 20},
          {'ticket_id': 4, 'event': 'Exhibition', 'price': 40}
      ]
  
  def create_reservation(ticket_id):
      return {'ticket_id': ticket_id, 'status': 'reserved'}
  
  def cancel_reservation(ticket_id):
      return {'ticket_id': ticket_id, 'status': 'cancelled'}