函数内部的模拟python函数

我有以下功能 script.py :

from mock import patch

def outer():
    def inner():
        # something here
        return 5
    return inner() + 2

print(outer())
# 7

outer 功能,我想模仿 inner

@patch("script.outer.inner")
def test_outer(mock_inner):
    mock_inner.return_value = 10

    result = outer()
    assert result == 12

AttributeError: <function outer at 0x10d594ae8> does not have the attribute 'inner' . 是我做错了什么还是这不可能?