物件具備 set 就代表此欄位可被改變，移除則代表此物件被建構後不可被改變。
Remove Setting Method
# Before
class Account:
def __init__(self, id):
self.id = id
def set_id(self, id):
self.id = id
account = Account(123)
account.set_id(456)
# After
class Account:
def __init__(self, id):
self.id = id
account = Account(123)
# id 在建構後就不可被改變