为什么我的嵌套函数不能在条件之后调用？

def outer_function():
    def nested_function():
        print("Nested function called")

    if condition:
        nested_function()  # 错误！嵌套函数在条件之后调用

condition = True
outer_function()

def outer_function():
    def nested_function():
        print("Nested function called")

    if condition:
        nested_function()  # 正确！嵌套函数在条件之前调用

condition = True
outer_function()

def nested_function():
    print("Nested function called")

def outer_function():
    if condition:
        nested_function()  # 正确！调用独立的嵌套函数

condition = True
outer_function()