Pytest unittest-style setup: module setup

Pytest documentation describes four ways to setup/teardown things:

• module level setup/teardown
• class level setup/teardown
• method level setup/teardown
• function level setup/teardown

But in one project it was implemented like this:

class TestClass:
    def setup(self):
        ...
    def test_1(self):
        ...
    ...

This setup method is called around each method invocation, just like setup_method from documentation (except that it doesn’t take method as an argument). But I haven’t seen it in the documentation or anywhere else. Why does it work?