当我想使用函数的返回值作为全局变量时，如何重构代码？

# my_module.py
global_var = None

def set_global_var(value):
    global global_var
    global_var = value

def get_global_var():
    return global_var

import my_module

def some_function():
    result = ...  # 计算结果
    my_module.set_global_var(result)

some_function()
print(my_module.get_global_var())

class GlobalState:
    def __init__(self):
        self._global_var = None

    def set_global_var(self, value):
        self._global_var = value

    def get_global_var(self):
        return self._global_var

# 创建一个全局实例
global_state = GlobalState()

def some_function():
    result = ...  # 计算结果
    global_state.set_global_var(result)

some_function()
print(global_state.get_global_var())

def some_function(global_var):
    result = ...  # 计算结果
    global_var.set(result)

class GlobalVar:
    def __init__(self):
        self.value = None

    def set(self, value):
        self.value = value

    def get(self):
        return self.value

global_var = GlobalVar()
some_function(global_var)
print(global_var.get())

def some_function(callback):
    result = ...  # 计算结果
    callback(result)

def handle_result(result):
    global global_var
    global_var = result

global_var = None
some_function(handle_result)
print(global_var)